1 00:00:02,000 --> 00:00:07,000 Downloaded from YTS.MX 2 00:00:08,000 --> 00:00:13,000 Official YIFY movies site: YTS.MX 3 00:00:22,600 --> 00:00:23,833 {\an1}We're warming the Earth 4 00:00:23,866 --> 00:00:27,433 {\an1}and the warming is causing a further warming. 5 00:00:30,433 --> 00:00:35,866 {\an1}Most people I know haven't even heard of feedback loops 6 00:00:35,900 --> 00:00:37,666 or tipping points, 7 00:00:37,700 --> 00:00:39,400 {\an1}but they are so crucial 8 00:00:39,433 --> 00:00:42,133 to understanding how the world works. 9 00:00:45,566 --> 00:00:48,400 As we started models in the late '50s, 10 00:00:48,433 --> 00:00:53,000 {\an1}we could find the climate changing in a pretty huge way. 11 00:00:54,200 --> 00:00:56,033 NARRATOR: Scientists have identified dozens 12 00:00:56,066 --> 00:00:59,200 of feedback loops already in motion. 13 00:00:59,233 --> 00:01:01,600 {\an1}Each amplifies warming 14 00:01:01,633 --> 00:01:04,700 {\an1}and, combined, they are spinning out of control. 15 00:01:07,866 --> 00:01:09,300 There were places where we walked 16 00:01:09,333 --> 00:01:11,700 where my foot fell into the ground 17 00:01:11,733 --> 00:01:14,433 {\an1}because there was no longer any ground structure, 18 00:01:14,466 --> 00:01:16,833 {\an1}because the permafrost was thawing. 19 00:01:24,233 --> 00:01:27,700 {\an1}Where we are now, it's like driving in a car in a dense fog 20 00:01:27,733 --> 00:01:30,566 {\an1}and you know there's a cliff out there somewhere, 21 00:01:30,600 --> 00:01:32,133 {\an1}but you don't know where. 22 00:01:35,500 --> 00:01:37,042 {\an1}Do you want to be going 60 miles an hour 23 00:01:37,066 --> 00:01:39,066 {\an1}or should you be going about ten miles an hour? 24 00:01:42,233 --> 00:01:44,533 NEW SPEAKER: The Earth will be just fine. 25 00:01:44,566 --> 00:01:47,766 {\an1}We may take along with us, unfortunately, 26 00:01:47,800 --> 00:01:49,700 {\an1}lots of different species. 27 00:01:51,866 --> 00:01:55,300 {\an1}I'm not worried about the planet. I'm worried about us. 28 00:02:00,200 --> 00:02:02,466 {\an1}NARRATOR: If we take action now, we could slow, 29 00:02:02,500 --> 00:02:05,166 halt or even reverse the climate crisis 30 00:02:05,200 --> 00:02:07,333 {\an1}before it's too late. 31 00:02:08,666 --> 00:02:12,266 {\an1}I'm optimistic by nature and I become more optimistic 32 00:02:12,300 --> 00:02:16,500 {\an1}when I see so many people that realize there's a problem. 33 00:02:23,833 --> 00:02:25,966 We can't allow it to be too late. 34 00:02:26,000 --> 00:02:27,700 It's time to act. 35 00:02:29,800 --> 00:02:31,466 {\an1}NARRATOR: If we don't, 36 00:02:31,500 --> 00:02:33,700 {\an1}the planet will reach a tipping point 37 00:02:33,733 --> 00:02:36,166 {\an1}where we will lose the world as we know it. 38 00:02:48,666 --> 00:02:49,933 Earth is warming... 39 00:02:53,933 --> 00:02:58,566 {\an1}..caused by the burning of fossil fuels like oil, coal 40 00:02:58,600 --> 00:03:01,500 and natural gas, filling the atmosphere 41 00:03:01,533 --> 00:03:04,933 {\an1}with heat-trapping gases like carbon dioxide, 42 00:03:04,966 --> 00:03:07,666 {\an1}methane, nitrous oxide 43 00:03:07,700 --> 00:03:10,200 at levels humans have never seen before. 44 00:03:11,966 --> 00:03:13,166 As the world debates 45 00:03:13,200 --> 00:03:16,133 how much more warming the planet can take... 46 00:03:16,166 --> 00:03:18,500 {\an1}One and a half degrees Celsius? 47 00:03:18,533 --> 00:03:20,933 Two degrees Celsius? 48 00:03:20,966 --> 00:03:23,233 {\an1}..the climate crisis escalates. 49 00:03:25,766 --> 00:03:27,600 {\an1}The problems are that the world 50 00:03:27,633 --> 00:03:31,166 {\an8}is becoming too hot for the present distribution 51 00:03:31,200 --> 00:03:34,500 {\an7}of people, agriculture, human welfare 52 00:03:34,533 --> 00:03:36,333 and human interest, 53 00:03:36,366 --> 00:03:38,866 {\an1}and it's getting worse. 54 00:03:38,900 --> 00:03:40,666 {\an1}NARRATOR: But it's more than our emissions 55 00:03:40,700 --> 00:03:41,800 heating the globe. 56 00:03:41,833 --> 00:03:44,066 {\an1}Something else is at work here. 57 00:03:44,100 --> 00:03:47,033 {\an1}The rising temperatures are setting in motion 58 00:03:47,066 --> 00:03:49,766 Earth's own natural warming mechanisms 59 00:03:49,800 --> 00:03:51,866 {\an1}that then feed upon themselves. 60 00:03:53,466 --> 00:03:55,900 George Woodwell, a distinguished scientist 61 00:03:55,933 --> 00:03:58,233 and a lion of the environmental movement, 62 00:03:58,266 --> 00:04:00,500 {\an1}has been sounding the alarm about them 63 00:04:00,533 --> 00:04:02,833 {\an1}for the past 50 years. 64 00:04:02,866 --> 00:04:05,566 {\an1}In a 1989 Scientific American article, 65 00:04:05,600 --> 00:04:08,966 {\an1}he wrote that warming caused by human activity, 66 00:04:09,000 --> 00:04:12,200 "rapid now, may become even more rapid 67 00:04:12,233 --> 00:04:15,400 "as a result of the warming itself." 68 00:04:15,433 --> 00:04:19,000 {\an8}30 years later, climate activist Greta Thunberg 69 00:04:19,033 --> 00:04:21,066 {\an1}repeated his warning, 70 00:04:21,100 --> 00:04:25,533 calling them "irreversible chain reactions". 71 00:04:25,566 --> 00:04:30,466 {\an7}The popular idea of cutting our emissions in half in ten years 72 00:04:30,500 --> 00:04:35,400 {\an7}only gives us a 50% chance of staying below 1.5 degrees 73 00:04:35,433 --> 00:04:38,866 {\an1}at the risk of setting off irreversible chain reactions 74 00:04:38,900 --> 00:04:40,466 {\an1}beyond human control. 75 00:04:41,666 --> 00:04:44,933 {\an1}50% may be acceptable to you... 76 00:04:46,066 --> 00:04:49,800 ..but those numbers do not include tipping points, 77 00:04:49,833 --> 00:04:51,433 most feedback loops, 78 00:04:51,466 --> 00:04:54,300 {\an1}additional warming hidden by toxic air pollution 79 00:04:54,333 --> 00:04:58,533 {\an1}or the aspects of equity and climate justice. 80 00:04:58,566 --> 00:05:02,466 {\an1}NARRATOR: So, what exactly are irreversible chain reactions, 81 00:05:02,500 --> 00:05:05,900 {\an1}what scientists refer to as feedback loops? 82 00:05:07,900 --> 00:05:11,200 {\an1}A feedback that everybody is familiar with 83 00:05:11,233 --> 00:05:12,866 is an audio feedback 84 00:05:12,900 --> 00:05:15,800 {\an7}where, if you put a microphone too close to a speaker, 85 00:05:15,833 --> 00:05:19,533 {\an7}you get this terrible high-pitched screaming. 86 00:05:19,566 --> 00:05:22,900 {\an1}And that happens because the sound comes out of the speaker 87 00:05:22,933 --> 00:05:24,966 and it goes back into the microphone. 88 00:05:25,000 --> 00:05:26,966 That's called a positive feedback 89 00:05:27,000 --> 00:05:29,100 {\an1}because it amplifies the loop. 90 00:05:30,533 --> 00:05:31,933 NARRATOR: Instead of the guitar, 91 00:05:31,966 --> 00:05:35,433 {\an1}emissions from fossil fuels are the input 92 00:05:35,466 --> 00:05:38,733 {\an7}which add heat-trapping gases to the atmosphere... 93 00:05:39,666 --> 00:05:41,100 {\an7}..and setting in motion 94 00:05:41,133 --> 00:05:44,566 {\an8}self-perpetuating warming loops - 95 00:05:44,600 --> 00:05:47,533 {\an8}warming as a result of the warming itself. 96 00:05:54,733 --> 00:05:58,333 {\an1}That ever-growing screeching noise is an apt analogy 97 00:05:58,366 --> 00:06:01,333 for the damage that human-caused feedback loops 98 00:06:01,366 --> 00:06:03,100 {\an1}are wreaking on the planet. 99 00:06:10,033 --> 00:06:12,733 {\an1}Scientists have identified dozens of feedback loops 100 00:06:12,766 --> 00:06:15,000 already in motion. 101 00:06:15,033 --> 00:06:16,866 It's imperative that we understand them 102 00:06:16,900 --> 00:06:19,133 {\an1}if we're going to solve the climate crisis. 103 00:06:23,833 --> 00:06:28,033 {\an1}As the climate warms, forests, once removers of carbon, 104 00:06:28,066 --> 00:06:29,800 release it back into the atmosphere 105 00:06:29,833 --> 00:06:32,333 {\an1}as carbon dioxide or CO2. 106 00:06:33,800 --> 00:06:36,733 Frozen ground in the Northern Hemisphere thaws 107 00:06:36,766 --> 00:06:39,066 {\an1}and emits CO2 and methane. 108 00:06:41,133 --> 00:06:44,000 {\an1}The melting of sea ice in the Arctic Ocean, 109 00:06:44,033 --> 00:06:47,933 {\an1}increased drought and fires in the world's forests, 110 00:06:47,966 --> 00:06:50,366 {\an1}a decay of organic matter 111 00:06:50,400 --> 00:06:53,600 from permafrost thaw in the Northern Hemisphere 112 00:06:53,633 --> 00:06:55,700 and disruptions to the jet stream 113 00:06:55,733 --> 00:06:57,266 {\an1}and our global weather. 114 00:06:58,733 --> 00:07:00,533 These are the kinds of feedback loops 115 00:07:00,566 --> 00:07:02,466 {\an1}that lead to further warming, 116 00:07:02,500 --> 00:07:06,233 {\an1}triggering the release of even more heat-trapping gases 117 00:07:06,266 --> 00:07:09,433 {\an1}and raising the temperature even higher. 118 00:07:12,200 --> 00:07:14,066 {\an1}Each amplifies warming 119 00:07:14,100 --> 00:07:17,066 {\an1}and, combined, they are spinning out of control. 120 00:07:19,200 --> 00:07:20,500 {\an1}If we take action now, 121 00:07:20,533 --> 00:07:23,266 we could slow, halt or even reverse them 122 00:07:23,300 --> 00:07:24,900 {\an1}before it's too late. 123 00:07:26,733 --> 00:07:27,933 If we don't... 124 00:07:29,300 --> 00:07:31,300 {\an1}..the planet will reach a tipping point... 125 00:07:32,566 --> 00:07:34,800 {\an1}..where we will lose the world as we know it. 126 00:07:39,633 --> 00:07:42,766 {\an1}With more than seven and a half billion people on Earth, 127 00:07:42,800 --> 00:07:46,533 a change this great would spell catastrophe. 128 00:07:49,000 --> 00:07:52,133 {\an1}Humans are well-suited to the world we've known. 129 00:07:52,166 --> 00:07:56,100 {\an1}The sun's radiation passes through atmospheric gases, 130 00:07:56,133 --> 00:07:59,500 {\an1}primarily oxygen and nitrogen, to the Earth's surface. 131 00:08:00,566 --> 00:08:02,833 {\an1}Some radiation is absorbed by the planet 132 00:08:02,866 --> 00:08:05,433 {\an1}and the rest would bounce back to space 133 00:08:05,466 --> 00:08:07,866 if it weren't for a tiny percentage of gases 134 00:08:07,900 --> 00:08:11,533 {\an1}like carbon dioxide, methane, water vapor and others 135 00:08:11,566 --> 00:08:14,933 that trap heat and warm the atmosphere. 136 00:08:14,966 --> 00:08:17,366 These heat-trapping greenhouse gases 137 00:08:17,400 --> 00:08:20,900 make up less than 1% of the total atmosphere, 138 00:08:20,933 --> 00:08:24,000 {\an1}but they are essential in regulating the temperature. 139 00:08:24,966 --> 00:08:26,700 {\an1}Without them, we would freeze, 140 00:08:26,733 --> 00:08:29,633 but too much of them would overheat the planet. 141 00:08:29,666 --> 00:08:31,300 Both are possible 142 00:08:31,333 --> 00:08:34,866 and have happened in Earth's geologic past. 143 00:08:36,733 --> 00:08:38,633 {\an1}So, the kind of things 144 00:08:38,666 --> 00:08:41,600 {\an1}that keep climate scientists awake at night 145 00:08:41,633 --> 00:08:43,733 {\an1}stem from their familiarity 146 00:08:43,766 --> 00:08:45,833 {\an1}with the geological record 147 00:08:45,866 --> 00:08:50,333 {\an1}that shows that the climate is capable of very abrupt changes. 148 00:08:50,366 --> 00:08:52,866 There are feedbacks operating in the climate system 149 00:08:52,900 --> 00:08:56,266 {\an1}that may temporarily go out of control, if you will, 150 00:08:56,300 --> 00:08:59,000 {\an1}and drive the climate to a different state. 151 00:09:00,433 --> 00:09:02,066 We cannot rule out 152 00:09:02,100 --> 00:09:05,866 that we may be in for such an abrupt change. 153 00:09:05,900 --> 00:09:08,566 {\an1}We don't fully understand them, 154 00:09:08,600 --> 00:09:11,566 {\an1}but we worry about that... a lot. 155 00:09:13,366 --> 00:09:14,900 NARRATOR: These radical changes 156 00:09:14,933 --> 00:09:17,566 include extreme temperature swings. 157 00:09:18,466 --> 00:09:20,166 {\an1}About 500 million years ago, 158 00:09:20,200 --> 00:09:22,600 there was a cycle of alternations 159 00:09:22,633 --> 00:09:25,400 {\an1}between a practically ice-covered planet 160 00:09:25,433 --> 00:09:27,466 {\an1}and a very hot planet. 161 00:09:28,700 --> 00:09:31,300 {\an1}NARRATOR: During periods known as Snowball Earth, 162 00:09:31,333 --> 00:09:32,400 it got so cold, 163 00:09:37,000 --> 00:09:39,966 These alternated with hothouse climates 164 00:09:40,000 --> 00:09:42,300 when virtually all the ice melted. 165 00:09:42,333 --> 00:09:43,766 {\an1}Dinosaurs lived at the poles 166 00:09:43,800 --> 00:09:46,600 where forests and swamps flourished. 167 00:09:50,666 --> 00:09:52,566 These abrupt shifts were caused 168 00:09:52,600 --> 00:09:55,466 {\an1}by complex global processes. 169 00:09:57,766 --> 00:10:00,900 {\an1}This is the first time that humans have been responsible 170 00:10:00,933 --> 00:10:02,466 {\an1}for an abrupt change. 171 00:10:06,166 --> 00:10:10,066 {\an1}Today, Earth would naturally be in a cooling trend, 172 00:10:10,100 --> 00:10:12,666 {\an1}but because of human activity, it's not. 173 00:10:14,666 --> 00:10:18,000 {\an1}KERRY EMANUEL: So, we know from paleo proxy records 174 00:10:18,033 --> 00:10:22,800 {\an1}that the Earth has been cooling for about 7,000 years. 175 00:10:22,833 --> 00:10:25,366 {\an1}We recovered from the peak of the last ice age, 176 00:10:25,400 --> 00:10:27,066 which was about 22,000 years ago, 177 00:10:27,100 --> 00:10:29,200 it went up and it's been slowly cooling 178 00:10:29,233 --> 00:10:33,933 {\an1}until about the time of the Industrial Revolution. 179 00:10:33,966 --> 00:10:36,400 {\an7}NARRATOR: At that time, humans began emitting 180 00:10:36,433 --> 00:10:39,033 {\an7}vast amounts of carbon dioxide. 181 00:10:39,066 --> 00:10:41,600 {\an8}Since then, the atmospheric content of CO2 182 00:10:41,633 --> 00:10:45,333 {\an7}has gone from 280 parts per million 183 00:10:45,366 --> 00:10:47,666 {\an8}to over 400 today 184 00:10:47,700 --> 00:10:51,166 {\an7}and could approach 800 by the end of the century. 185 00:10:53,233 --> 00:10:56,166 {\an1}Of all the carbon dioxide humans emit each year, 186 00:10:56,200 --> 00:10:59,133 oceans absorb about one quarter, 187 00:10:59,166 --> 00:11:01,600 {\an1}plants take up another quarter 188 00:11:01,633 --> 00:11:04,166 {\an1}and the other half stays in the atmosphere, 189 00:11:04,200 --> 00:11:08,166 {\an1}accumulating over time and raising Earth's temperature. 190 00:11:11,800 --> 00:11:15,333 {\an1}But the percentage nature removes is shrinking 191 00:11:15,366 --> 00:11:18,100 {\an1}as forests are destroyed and oceans warm. 192 00:11:23,900 --> 00:11:26,900 Scientists estimate that doubling CO2 193 00:11:26,933 --> 00:11:28,400 {\an1}from pre-industrial levels 194 00:11:28,433 --> 00:11:31,033 could produce an increase in temperature 195 00:11:31,066 --> 00:11:33,733 {\an1}of up to eight degrees Fahrenheit... 196 00:11:35,566 --> 00:11:38,866 {\an1}..resulting in the deaths of millions of people 197 00:11:38,900 --> 00:11:41,333 and the loss of countless species. 198 00:11:46,500 --> 00:11:48,566 {\an1}It's this human-caused warming 199 00:11:48,600 --> 00:11:51,933 {\an1}that is kicking off Earth's natural feedback loops 200 00:11:51,966 --> 00:11:54,066 {\an1}and heating up the planet further. 201 00:11:59,933 --> 00:12:03,200 {\an1}National Medal of Science recipient Warren Washington, 202 00:12:03,233 --> 00:12:05,366 a ground-breaking climate pioneer, 203 00:12:05,400 --> 00:12:08,300 {\an1}began creating computer models in the 1960s 204 00:12:08,333 --> 00:12:11,433 to predict the future of atmospheric warming 205 00:12:11,466 --> 00:12:13,600 and the role feedback loops play. 206 00:12:14,733 --> 00:12:17,000 WARREN WASHINGTON: The question always was, 207 00:12:17,033 --> 00:12:18,466 how do we see 208 00:12:18,500 --> 00:12:22,900 {\an1}the feedback mechanisms working realistically? 209 00:12:22,933 --> 00:12:26,833 {\an8}We really don't know if we got the right amount 210 00:12:26,866 --> 00:12:30,666 {\an7}of feedback in our models... 211 00:12:30,700 --> 00:12:33,933 {\an1}..because they are so complicated in many cases. 212 00:12:33,966 --> 00:12:36,066 We had to do a lot of experimenting. 213 00:12:39,200 --> 00:12:41,866 {\an1}NARRATOR: That experimenting, coupled with observations, 214 00:12:41,900 --> 00:12:42,900 paid off. 215 00:12:42,933 --> 00:12:44,100 {\an1}Because of that ground work, 216 00:12:44,133 --> 00:12:47,400 today's models have more accurately predicted 217 00:12:47,433 --> 00:12:49,100 {\an1}what our future holds. 218 00:12:51,233 --> 00:12:52,833 {\an1}This kind of research is crucial 219 00:12:52,866 --> 00:12:56,033 {\an1}to understanding the policies we need to implement 220 00:12:56,066 --> 00:12:58,466 to avoid disaster going forward. 221 00:12:59,766 --> 00:13:02,533 {\an8}Climate policy really should be designed 222 00:13:02,566 --> 00:13:04,833 {\an8}to avoid crossing the important thresholds, 223 00:13:04,866 --> 00:13:07,033 {\an8}avoid crossing the important tipping points 224 00:13:07,066 --> 00:13:10,900 {\an1}and avoid setting off these important feedbacks 225 00:13:10,933 --> 00:13:13,800 {\an1}because we need to essentially ask the question, 226 00:13:13,833 --> 00:13:15,000 {\an1}how much warming is OK? 227 00:13:15,033 --> 00:13:17,300 {\an1}Is two degrees OK? Is one and a half degrees OK? 228 00:13:17,333 --> 00:13:19,733 {\an1}We really don't know the answer to that very well. 229 00:13:20,833 --> 00:13:22,666 (BIRDS SINGING) 230 00:13:23,533 --> 00:13:25,166 NARRATOR: Trees play a vital role 231 00:13:25,200 --> 00:13:27,166 {\an1}in the health of the planet. 232 00:13:27,200 --> 00:13:28,466 {\an1}Through photosynthesis, 233 00:13:28,500 --> 00:13:30,466 they help regulate Earth's temperature 234 00:13:30,500 --> 00:13:33,933 {\an1}by pulling carbon dioxide, a powerful heat-trapping gas, 235 00:13:33,966 --> 00:13:37,333 from the atmosphere and emitting oxygen. 236 00:13:38,666 --> 00:13:41,366 {\an1}Since carbon dioxide warms the atmosphere, 237 00:13:41,400 --> 00:13:45,100 {\an1}by removing it and storing much of the carbon safely away 238 00:13:45,133 --> 00:13:49,933 {\an1}in their branches, trunks, leaves, roots and soils, 239 00:13:49,966 --> 00:13:52,400 {\an1}forests help cool the Earth. 240 00:13:53,766 --> 00:13:55,100 {\an8}In fact, every year, 241 00:13:55,133 --> 00:13:57,966 {\an7}terrestrial ecosystems remove about 30% 242 00:13:58,000 --> 00:13:59,766 {\an7}of fossil fuel emissions 243 00:13:59,800 --> 00:14:02,300 {\an7}and forests are responsible for most of that. 244 00:14:03,233 --> 00:14:05,500 {\an8}But that percentage is decreasing 245 00:14:05,533 --> 00:14:07,333 {\an7}as emissions increase, 246 00:14:07,366 --> 00:14:09,166 {\an8}steadily raising Earth's temperature 247 00:14:09,200 --> 00:14:12,833 {\an7}and threatening forests' ability to offset the warming. 248 00:14:17,100 --> 00:14:21,700 {\an1}We have warmed the Earth by a full degree and a little more 249 00:14:21,733 --> 00:14:27,033 {\an1}and forests are suffering increased hazards of fire 250 00:14:27,066 --> 00:14:29,400 {\an1}as they get warm and dry... 251 00:14:30,400 --> 00:14:34,033 ..increased hazards of disease... 252 00:14:34,066 --> 00:14:37,466 {\an1}..as they become vulnerable to insects... 253 00:14:38,466 --> 00:14:40,666 {\an1}..and dying as a result. 254 00:14:43,200 --> 00:14:45,100 NARRATOR: As trees die, they become part 255 00:14:45,133 --> 00:14:48,500 {\an1}of a dangerous feedback loop kicked off by the warming. 256 00:14:50,333 --> 00:14:51,800 {\an1}As the temperature rises, 257 00:14:51,833 --> 00:14:54,066 {\an1}the climate becomes hotter and drier 258 00:14:54,100 --> 00:14:55,400 and they fall prey 259 00:14:55,433 --> 00:14:57,733 {\an1}to drought, fire and insects. 260 00:14:59,266 --> 00:15:00,566 {\an1}The fewer trees left, 261 00:15:00,600 --> 00:15:02,166 {\an1}the more heat-trapping gas 262 00:15:02,200 --> 00:15:03,800 {\an1}remains in the atmosphere, 263 00:15:03,833 --> 00:15:05,533 {\an1}raising the temperature higher, 264 00:15:05,566 --> 00:15:08,166 {\an1}resulting in even more dieback. 265 00:15:10,233 --> 00:15:11,733 {\an1}As trees burn and decay, 266 00:15:11,766 --> 00:15:15,066 {\an1}the carbon they've locked away during their lifetime, 267 00:15:15,100 --> 00:15:17,766 what scientists call a "carbon sink", 268 00:15:17,800 --> 00:15:20,100 {\an1}is released back into the air. 269 00:15:23,433 --> 00:15:26,233 {\an1}GEORGE WOODWELL: It's entirely possible we reach a point 270 00:15:26,266 --> 00:15:29,233 {\an1}where we're killing off forests much more rapidly 271 00:15:29,266 --> 00:15:32,433 {\an1}than carbon can be fixed by forests. 272 00:15:32,466 --> 00:15:37,266 The net result then is to produce a feedback 273 00:15:37,300 --> 00:15:38,833 that's lethal. 274 00:15:38,866 --> 00:15:40,966 (BIRDS SINGING) 275 00:15:43,100 --> 00:15:44,933 NARRATOR: Today, we have a choice - 276 00:15:44,966 --> 00:15:48,033 {\an1}allow trees to do their job and cool the planet 277 00:15:48,066 --> 00:15:51,166 {\an1}or jeopardize the forests we have. 278 00:15:51,200 --> 00:15:53,033 That's the path we're on right now. 279 00:15:53,866 --> 00:15:55,933 How we protect and manage forests 280 00:15:55,966 --> 00:15:59,000 {\an1}will play a large role in determining our future. 281 00:16:02,266 --> 00:16:03,800 When it comes to global warming, 282 00:16:03,833 --> 00:16:06,400 three major forests matter the most - 283 00:16:06,433 --> 00:16:10,833 {\an1}the tropical, the boreal and the temperate. 284 00:16:10,866 --> 00:16:13,900 {\an1}No forest is more critical for cooling the planet 285 00:16:13,933 --> 00:16:15,533 than the Amazon. 286 00:16:15,566 --> 00:16:18,800 Spanning more than two million square miles 287 00:16:18,833 --> 00:16:20,733 {\an1}across nine countries, 288 00:16:20,766 --> 00:16:25,266 {\an1}this tropical forest has been storing carbon for millennia, 289 00:16:25,300 --> 00:16:27,633 {\an1}yet it is dangerously close 290 00:16:27,666 --> 00:16:30,900 {\an1}to releasing more carbon than it absorbs. 291 00:16:37,233 --> 00:16:40,266 {\an1}Mike Coe is the Director of the Tropics Program 292 00:16:40,300 --> 00:16:43,000 at the Woodwell Climate Research Center. 293 00:16:45,100 --> 00:16:46,866 For over 20 years, he has studied 294 00:16:46,900 --> 00:16:49,533 how deforestation in the Amazon rainforest 295 00:16:49,566 --> 00:16:52,400 {\an1}affects the local climate and environment. 296 00:16:54,466 --> 00:16:56,633 {\an1}MIKE COE: Tropical rainforests probably account 297 00:16:56,666 --> 00:17:02,433 {\an1}for about 15 to 20% of all the terrestrial carbon sink 298 00:17:02,466 --> 00:17:04,366 {\an7}and the Amazon is half of that. 299 00:17:04,400 --> 00:17:06,433 {\an8}So, we're talking about a significant fraction 300 00:17:06,466 --> 00:17:08,233 {\an7}of our annual emissions are being taken up 301 00:17:08,266 --> 00:17:09,433 {\an7}by the Amazon forest. 302 00:17:09,466 --> 00:17:11,366 NARRATOR: But in the last 50 years, 303 00:17:11,400 --> 00:17:14,600 {\an1}nearly 20% of this forest has been lost, 304 00:17:14,633 --> 00:17:17,400 {\an1}mostly to slash-and-burn land clearing, 305 00:17:17,433 --> 00:17:22,066 {\an1}triggering fires, insects and tree dieback. 306 00:17:22,100 --> 00:17:24,900 {\an1}This not only releases the carbon stored there, 307 00:17:24,933 --> 00:17:27,733 it jeopardizes an important cooling function 308 00:17:27,766 --> 00:17:29,533 {\an1}of the Amazon rainforest. 309 00:17:30,966 --> 00:17:32,600 {\an1}During transpiration, 310 00:17:32,633 --> 00:17:34,633 roots pull water out of the ground 311 00:17:34,666 --> 00:17:37,133 {\an1}and release it as water vapor 312 00:17:37,166 --> 00:17:39,933 {\an1}through tiny holes in the tree's leaves, 313 00:17:39,966 --> 00:17:43,300 {\an1}creating a cooling effect on the surrounding air. 314 00:17:43,333 --> 00:17:46,200 {\an1}In the Amazon, transpiration can cool the region 315 00:17:46,233 --> 00:17:49,200 by as much as ten degrees Fahrenheit. 316 00:17:52,033 --> 00:17:53,833 {\an1}MIKE COE: When we lose trees in the Amazon, 317 00:17:53,866 --> 00:17:55,500 {\an1}when we cut them down, what we're doing 318 00:17:55,533 --> 00:17:57,633 {\an1}is we're shutting off that transpiration, 319 00:17:57,666 --> 00:17:59,866 so what you get is a drier climate. 320 00:17:59,900 --> 00:18:02,533 {\an1}And the more you deforest, the drier it gets. 321 00:18:03,533 --> 00:18:05,133 NARRATOR: Over the past two decades, 322 00:18:05,166 --> 00:18:07,933 {\an1}the dry season has extended several weeks, 323 00:18:07,966 --> 00:18:09,500 {\an1}stressing trees even more... 324 00:18:10,800 --> 00:18:13,300 ..and creating an ideal environment 325 00:18:13,333 --> 00:18:14,900 for fires to spread. 326 00:18:16,800 --> 00:18:18,300 MIKE COE: During extreme droughts, 327 00:18:18,333 --> 00:18:20,200 a huge amount of the forest burns. 328 00:18:20,233 --> 00:18:23,033 {\an1}That turns the forest that year from a net sink 329 00:18:23,066 --> 00:18:24,700 {\an1}to a net source of carbon. 330 00:18:24,733 --> 00:18:26,033 We can do the math. 331 00:18:26,066 --> 00:18:28,166 If that happens five times a decade, 332 00:18:28,200 --> 00:18:31,633 {\an1}this forest is now a source. 333 00:18:31,666 --> 00:18:34,100 {\an8}NARRATOR: Today, tropical forests are absorbing 334 00:18:34,133 --> 00:18:36,200 {\an7}one-third less carbon 335 00:18:36,233 --> 00:18:39,300 {\an7}than they did in the 1990s. 336 00:18:39,333 --> 00:18:42,500 {\an7}Scientists predict that with the loss of so many trees, 337 00:18:42,533 --> 00:18:47,000 {\an1}the Amazon could flip to emitting more carbon 338 00:18:47,033 --> 00:18:50,466 than it stores as soon as the next decade. 339 00:18:57,700 --> 00:18:59,966 {\an1}The next major forest at risk of tipping 340 00:19:00,000 --> 00:19:03,100 from a carbon sink to a carbon source 341 00:19:03,133 --> 00:19:05,933 is the boreal encircling the North Pole 342 00:19:05,966 --> 00:19:08,200 through Siberia and North America. 343 00:19:10,500 --> 00:19:12,833 {\an1}The largest forested region in the world, 344 00:19:12,866 --> 00:19:15,100 {\an1}this vast coniferous expanse 345 00:19:15,133 --> 00:19:19,166 {\an1}stores an estimated two-thirds of all forest carbon, 346 00:19:19,200 --> 00:19:22,966 {\an1}most of it locked away in frozen plant and animal remains 347 00:19:23,000 --> 00:19:25,000 deep in the ground. 348 00:19:25,033 --> 00:19:26,866 But that's changing. 349 00:19:26,900 --> 00:19:28,400 {\an1}As with tropical forests, 350 00:19:28,433 --> 00:19:30,500 {\an1}the warmer, drier climate here 351 00:19:30,533 --> 00:19:33,400 is making the trees more vulnerable to disease, 352 00:19:33,433 --> 00:19:35,500 insects and fire. 353 00:19:37,166 --> 00:19:40,233 {\an1}Brendan Rogers has been studying how boreal forests 354 00:19:40,266 --> 00:19:43,066 {\an1}respond to climate change for the past decade. 355 00:19:43,100 --> 00:19:45,900 {\an1}Wildfires are getting worse across the boreal zone. 356 00:19:45,933 --> 00:19:48,133 {\an7}We're seeing more and more large fire seasons, 357 00:19:48,166 --> 00:19:51,500 {\an7}record-breaking fire seasons every year. 358 00:19:51,533 --> 00:19:53,400 NARRATOR: Unlike in tropical forests, 359 00:19:53,433 --> 00:19:56,900 {\an1}the fires here strip off the insulating ground cover, 360 00:19:56,933 --> 00:20:00,600 {\an1}preventing it from building up in between the frequent burns. 361 00:20:01,633 --> 00:20:03,000 {\an1}Without this protective layer, 362 00:20:03,033 --> 00:20:06,000 fires reach further and further down, 363 00:20:06,033 --> 00:20:09,233 {\an1}burning the organic matter stored in the soil. 364 00:20:10,166 --> 00:20:11,833 About 75 to 90% 365 00:20:11,866 --> 00:20:14,900 {\an1}of all the carbon stored in these forests is underground 366 00:20:14,933 --> 00:20:16,866 and that is actually the majority of the carbon 367 00:20:16,900 --> 00:20:19,833 {\an1}that's getting released from these fires. 368 00:20:19,866 --> 00:20:21,966 {\an1}NARRATOR: The fires kick off a feedback loop, 369 00:20:22,000 --> 00:20:24,833 triggered by warming in the boreal zone. 370 00:20:24,866 --> 00:20:27,633 {\an1}More fires burn carbon deeper down in the soil, 371 00:20:27,666 --> 00:20:32,233 {\an1}releasing carbon dioxide and methane into the atmosphere, 372 00:20:32,266 --> 00:20:35,866 {\an1}heat-trapping gases that make the climate hotter and drier, 373 00:20:35,900 --> 00:20:38,000 {\an1}leading to more wildfires. 374 00:20:40,666 --> 00:20:43,566 {\an1}Like the Amazon, the boreal forest is going to switch 375 00:20:43,600 --> 00:20:46,333 from a carbon sink to a carbon source. 376 00:20:47,300 --> 00:20:49,100 {\an1}Scientists don't know exactly when, 377 00:20:49,133 --> 00:20:51,366 but predict that at the current rate, 378 00:20:51,400 --> 00:20:53,700 it will happen by the end of this century... 379 00:20:54,600 --> 00:20:56,066 {\an1}..crossing a tipping point 380 00:20:56,100 --> 00:20:59,233 that the forest can no longer recover from. 381 00:20:59,266 --> 00:21:02,100 {\an1}The scary thing is not knowing where that tipping point is. 382 00:21:03,500 --> 00:21:05,633 (DISTANT BIRDS CRY) 383 00:21:12,800 --> 00:21:14,833 NARRATOR: The temperate forest makes up 384 00:21:14,866 --> 00:21:17,200 only one quarter of the world's forests, 385 00:21:17,233 --> 00:21:18,533 {\an1}but it's our best hope 386 00:21:18,566 --> 00:21:21,500 {\an1}since the tropical and boreal forests are on the brink 387 00:21:21,533 --> 00:21:23,933 {\an1}of becoming emitters of carbon. 388 00:21:23,966 --> 00:21:25,566 (BIRDS SINGING) 389 00:21:26,866 --> 00:21:28,733 {\an1}Once cleared for agriculture, 390 00:21:28,766 --> 00:21:31,566 {\an1}many temperate forests in the US and Europe 391 00:21:31,600 --> 00:21:33,766 have made a comeback in recent decades. 392 00:21:35,500 --> 00:21:38,400 {\an1}But in the south-eastern US, old forests are being cut down 393 00:21:38,433 --> 00:21:41,566 {\an1}by the wood pellet industry for burning, 394 00:21:41,600 --> 00:21:45,633 {\an1}releasing decades of stored carbon back into the air. 395 00:21:46,900 --> 00:21:49,333 {\an1}Even though these forests are being replanted, 396 00:21:49,366 --> 00:21:51,666 {\an1}when it comes to offsetting global warming, 397 00:21:51,700 --> 00:21:54,766 {\an1}old and young forests are not equal. 398 00:21:57,300 --> 00:21:59,366 {\an1}Beverly Law has been measuring the exchange 399 00:21:59,400 --> 00:22:02,133 {\an1}of both carbon dioxide and water 400 00:22:02,166 --> 00:22:04,633 between our forests and our atmosphere 401 00:22:04,666 --> 00:22:06,266 {\an1}for the last 25 years. 402 00:22:08,266 --> 00:22:10,666 {\an1}In a young forest ecosystem, 403 00:22:10,700 --> 00:22:12,633 {\an8}there aren't that many trees there 404 00:22:12,666 --> 00:22:16,666 {\an7}and they're not taking up much carbon from the atmosphere. 405 00:22:18,533 --> 00:22:21,533 An older forest has a lot of carbon stored 406 00:22:21,566 --> 00:22:23,466 {\an1}compared to a younger forest. 407 00:22:25,233 --> 00:22:28,300 {\an1}If I were to try and mitigate climate change, 408 00:22:28,333 --> 00:22:30,966 my best strategy is when you have forests 409 00:22:31,000 --> 00:22:34,666 {\an1}that have low vulnerability to climate change in the future 410 00:22:34,700 --> 00:22:37,133 and they store a lot of carbon already 411 00:22:37,166 --> 00:22:40,733 {\an1}is to keep those forests like they are, preserve them. 412 00:22:43,833 --> 00:22:45,333 NARRATOR: When a tree is logged, 413 00:22:45,366 --> 00:22:47,466 {\an1}one half to two thirds of the carbon it stores 414 00:22:47,500 --> 00:22:49,933 {\an1}is released through decay 415 00:22:49,966 --> 00:22:53,300 {\an1}or burning of the unused branches, leaves and roots, 416 00:22:53,333 --> 00:22:56,700 as well as from the surrounding soil. 417 00:22:56,733 --> 00:23:00,866 Today, 17% of global carbon emissions each year 418 00:23:00,900 --> 00:23:02,933 {\an1}can be attributed to logging 419 00:23:02,966 --> 00:23:05,866 {\an1}and burning wood pellets for bioenergy. 420 00:23:07,366 --> 00:23:08,533 {\an1}BEVERLY LAW: In Oregon, 421 00:23:08,566 --> 00:23:12,800 {\an1}of all the forest harvested over the past 100 years, 422 00:23:12,833 --> 00:23:18,233 {\an1}65% of that carbon has gone back to the atmosphere. 423 00:23:18,266 --> 00:23:21,766 {\an1}This is just the wrong time for that in terms of climate. 424 00:23:26,833 --> 00:23:28,333 NARRATOR: With the clock ticking, 425 00:23:28,366 --> 00:23:32,033 {\an1}it comes down to how we manage temperate forests - 426 00:23:32,066 --> 00:23:35,100 use them for commercial purposes 427 00:23:35,133 --> 00:23:38,100 or keep them intact to cool the planet. 428 00:23:41,333 --> 00:23:45,300 {\an1}If we decide that we really are going to stabilize 429 00:23:45,333 --> 00:23:47,133 {\an1}or even cool the Earth, 430 00:23:47,166 --> 00:23:51,800 {\an1}we will have to rebuild forests around the world. 431 00:24:00,333 --> 00:24:02,100 NARRATOR: In the Northern Hemisphere, 432 00:24:02,133 --> 00:24:04,700 {\an1}nearly one quarter of the land is covered 433 00:24:04,733 --> 00:24:09,333 by an icy expanse called permafrost. 434 00:24:09,366 --> 00:24:12,066 {\an1}Extending from the surface down thousands of feet, 435 00:24:12,100 --> 00:24:14,433 its soil contains billions of tonnes 436 00:24:14,466 --> 00:24:18,033 of carbon-rich plant and animal remains, 437 00:24:18,066 --> 00:24:21,266 suspended in a perpetually frozen state. 438 00:24:23,000 --> 00:24:25,566 {\an1}But now, with human activity warming the Arctic 439 00:24:25,600 --> 00:24:29,033 {\an1}two to three times faster than the rest of the globe, 440 00:24:29,066 --> 00:24:31,633 this permafrost is starting to thaw. 441 00:24:32,900 --> 00:24:35,866 {\an1}And alarmingly, it contains twice as much carbon 442 00:24:35,900 --> 00:24:37,700 {\an1}as in the atmosphere today... 443 00:24:38,666 --> 00:24:40,000 {\an1}..and three times as much 444 00:24:40,033 --> 00:24:42,866 {\an1}as in all the world's forests combined. 445 00:24:47,466 --> 00:24:51,433 {\an1}As it thaws, microscopic animals called microbes 446 00:24:51,466 --> 00:24:54,866 {\an1}that have been frozen for up to tens of thousands of years 447 00:24:54,900 --> 00:24:56,233 are waking up 448 00:24:56,266 --> 00:24:59,433 {\an1}and feeding on the newly thawed carbon remains, 449 00:24:59,466 --> 00:25:03,366 emitting dangerous heat-trapping gases. 450 00:25:03,400 --> 00:25:06,433 {\an1}If we were to take all of the microbes on Earth, 451 00:25:06,466 --> 00:25:09,733 {\an7}we'd find that they'd weigh probably 50 times more 452 00:25:09,766 --> 00:25:12,633 {\an7}than all of the animals on Earth. 453 00:25:13,566 --> 00:25:15,300 {\an1}Now, these microbes need to eat 454 00:25:15,333 --> 00:25:20,200 {\an1}and what they eat are the dead remains of plants and animals. 455 00:25:20,233 --> 00:25:23,466 And as a by-product of feeding on that material, 456 00:25:23,500 --> 00:25:26,166 {\an1}they produce carbon dioxide and methane. 457 00:25:28,566 --> 00:25:31,566 {\an1}It's like having a chicken in your freezer, 458 00:25:31,600 --> 00:25:33,766 {\an7}you take the chicken out, you put it on the counter 459 00:25:33,800 --> 00:25:35,000 {\an7}and it starts to thaw. 460 00:25:35,033 --> 00:25:36,333 {\an8}Then you go away for the weekend 461 00:25:36,366 --> 00:25:38,209 {\an7}and you forgot about the chicken on the counter, 462 00:25:38,233 --> 00:25:39,933 you come back and the house smells, 463 00:25:39,966 --> 00:25:42,400 {\an1}the chicken's decomposed. 464 00:25:42,433 --> 00:25:45,466 {\an1}That's what happens to the carbon that's in permafrost. 465 00:25:45,500 --> 00:25:48,100 {\an1}It's fuel for microbes. 466 00:25:48,133 --> 00:25:50,300 {\an1}And as they're breaking it down and using that fuel, 467 00:25:50,333 --> 00:25:52,466 they're releasing greenhouse gases, 468 00:25:52,500 --> 00:25:54,900 {\an1}carbon dioxide and methane, into the atmosphere. 469 00:25:56,200 --> 00:25:58,300 NARRATOR: Driven by fossil fuel emissions 470 00:25:58,333 --> 00:26:00,233 {\an1}raising the temperature in the Arctic, 471 00:26:00,266 --> 00:26:03,133 {\an1}these microbes are amplifying the warming 472 00:26:03,166 --> 00:26:04,800 {\an1}as the permafrost thaws 473 00:26:04,833 --> 00:26:07,300 by releasing more carbon dioxide and methane 474 00:26:07,333 --> 00:26:09,366 into the atmosphere 475 00:26:09,400 --> 00:26:12,000 {\an1}and warming the climate even more 476 00:26:12,033 --> 00:26:13,933 {\an1}in a self-perpetuating loop. 477 00:26:15,666 --> 00:26:18,500 Which of these heat-trapping gases is released 478 00:26:18,533 --> 00:26:20,000 {\an1}depends on the environment 479 00:26:20,033 --> 00:26:23,000 {\an1}in which microbes digest the carbon. 480 00:26:23,033 --> 00:26:27,000 {\an7}In oxygen-rich conditions like soil and lake surfaces, 481 00:26:27,033 --> 00:26:30,766 {\an7}microbes produce carbon dioxide as a by-product. 482 00:26:31,700 --> 00:26:33,466 {\an8}But in environments lacking oxygen 483 00:26:33,500 --> 00:26:35,633 {\an8}like bogs and muddy lake bottoms, 484 00:26:35,666 --> 00:26:37,833 {\an8}they produce methane 485 00:26:37,866 --> 00:26:40,100 {\an7}which is nearly 30 times more potent 486 00:26:40,133 --> 00:26:42,666 {\an8}at trapping heat than carbon dioxide. 487 00:26:48,400 --> 00:26:50,533 The amount of carbon that could be released 488 00:26:50,566 --> 00:26:53,066 {\an1}from thawing permafrost by the end of this century 489 00:26:53,100 --> 00:26:58,266 {\an1}has been estimated to be up to 150 billion tonnes of carbon. 490 00:26:58,300 --> 00:27:01,233 {\an1}So, to put that in context, the US is currently 491 00:27:01,266 --> 00:27:04,000 {\an1}the second largest greenhouse gas emitting country 492 00:27:04,033 --> 00:27:05,266 in the world. 493 00:27:06,133 --> 00:27:08,100 If we took our current US emissions 494 00:27:08,133 --> 00:27:10,066 {\an1}and added that up through 2100, 495 00:27:10,100 --> 00:27:12,266 this is on par with the amount of carbon 496 00:27:12,300 --> 00:27:15,366 {\an1}that might be released from thawing permafrost. 497 00:27:17,300 --> 00:27:18,966 NARRATOR: Last summer, while working 498 00:27:19,000 --> 00:27:21,133 {\an1}in her usual field location in Alaska, 499 00:27:21,166 --> 00:27:24,166 Natali witnessed a remarkable acceleration 500 00:27:24,200 --> 00:27:25,966 {\an1}of permafrost melting. 501 00:27:27,466 --> 00:27:29,433 {\an1}SUE NATALI: First of all, it was very, very warm. 502 00:27:29,466 --> 00:27:31,733 {\an1}It was 90 degrees Fahrenheit in the tundra. 503 00:27:31,766 --> 00:27:33,466 There were places where we walked 504 00:27:33,500 --> 00:27:35,466 where my foot fell into the ground 505 00:27:35,500 --> 00:27:38,066 {\an1}because there was no longer any ground structure, 506 00:27:38,100 --> 00:27:40,666 {\an1}because the permafrost was thawing. 507 00:27:40,700 --> 00:27:43,700 {\an1}I've never seen change happening that quickly 508 00:27:43,733 --> 00:27:45,666 {\an1}from one year to the next. 509 00:27:45,700 --> 00:27:47,366 NARRATOR: The thawing permafrost 510 00:27:47,400 --> 00:27:49,966 {\an1}can entirely transform the landscape, 511 00:27:50,000 --> 00:27:53,766 {\an1}as Natali has seen in Duvanny Yar, Russia. 512 00:27:53,800 --> 00:27:57,333 {\an1}SUE NATALI: I had never seen permafrost thaw 513 00:27:57,366 --> 00:28:01,000 and ground collapse of that magnitude. 514 00:28:04,333 --> 00:28:06,600 {\an1}You see these really, really fine roots 515 00:28:06,633 --> 00:28:10,300 {\an1}that have been frozen for 40,000 years. 516 00:28:10,333 --> 00:28:13,233 Once they're thawed, they'll decompose in a year. 517 00:28:15,000 --> 00:28:17,566 {\an1}NARRATOR: And something else is having a dramatic effect 518 00:28:17,600 --> 00:28:20,033 {\an1}on the landscape in Siberia - 519 00:28:20,066 --> 00:28:22,866 {\an1}crater-like holes which are thought to be the result 520 00:28:22,900 --> 00:28:26,833 {\an1}of a build-up of methane under a thick layer of ice. 521 00:28:28,966 --> 00:28:31,000 When the ice melts, the pressure gives way, 522 00:28:31,033 --> 00:28:32,766 {\an1}causing an explosion. 523 00:28:33,833 --> 00:28:36,400 A year or two later, the craters form lakes 524 00:28:36,433 --> 00:28:38,900 that release the previously buried methane 525 00:28:38,933 --> 00:28:40,566 into the atmosphere. 526 00:28:44,066 --> 00:28:47,033 {\an1}Sometimes lakes that form from shifts in the landscape 527 00:28:47,066 --> 00:28:49,233 {\an1}emit so much methane, 528 00:28:49,266 --> 00:28:51,033 {\an1}you can light them on fire. 529 00:28:57,200 --> 00:28:58,433 {\an1}As the permafrost thaws 530 00:28:58,466 --> 00:29:02,033 {\an1}and the Arctic heats up faster than the rest of the planet, 531 00:29:02,066 --> 00:29:05,400 {\an1}that blanket of warming mixes into the atmosphere, 532 00:29:05,433 --> 00:29:06,766 encircles the globe 533 00:29:06,800 --> 00:29:10,000 {\an1}and it leads to all kinds of global disasters. 534 00:29:11,100 --> 00:29:13,400 {\an1}Crop failure in the Midwest. 535 00:29:14,533 --> 00:29:16,966 {\an1}Droughts and flooding in Africa. 536 00:29:18,500 --> 00:29:20,566 {\an1}Record heatwaves in India. 537 00:29:24,866 --> 00:29:26,300 {\an1}And in the Northern Hemisphere, 538 00:29:26,333 --> 00:29:28,600 home to most of the world's lakes, 539 00:29:28,633 --> 00:29:32,233 {\an1}the warming is having an impact similar to the permafrost thaw 540 00:29:32,266 --> 00:29:35,833 {\an1}by bringing new food sources to the microbes that live there. 541 00:29:39,133 --> 00:29:41,400 Plant species from south of this region 542 00:29:41,433 --> 00:29:45,133 {\an1}are migrating north, setting off another feedback loop. 543 00:29:46,300 --> 00:29:48,333 ANDREW TANENTZAP: Traditionally, the pine needles 544 00:29:48,366 --> 00:29:50,133 that the microbes would be digesting 545 00:29:50,166 --> 00:29:52,833 would have provided quite a limited diversity 546 00:29:52,866 --> 00:29:54,433 of food sources, 547 00:29:54,466 --> 00:29:57,166 {\an1}but now with deciduous broad-leaf species 548 00:29:57,200 --> 00:29:58,566 like maple and oak, 549 00:29:58,600 --> 00:30:01,766 {\an1}that's bringing a much greater diversity of organic matter 550 00:30:01,800 --> 00:30:04,366 and carbon for microbes to digest. 551 00:30:05,500 --> 00:30:07,000 NARRATOR: More food choices means 552 00:30:07,033 --> 00:30:09,066 an increase in microbial activity 553 00:30:09,100 --> 00:30:12,166 {\an1}which, in muddy lake bottoms lacking oxygen, 554 00:30:12,200 --> 00:30:15,633 {\an7}leads to methane production, a warmer climate 555 00:30:15,666 --> 00:30:17,166 {\an7}and more greening of lakes 556 00:30:17,200 --> 00:30:19,633 {\an7}in an ever-amplifying loop. 557 00:30:20,866 --> 00:30:22,233 {\an7}And the geographical range 558 00:30:22,266 --> 00:30:24,100 {\an7}where this dynamic is happening 559 00:30:24,133 --> 00:30:25,566 {\an8}is expanding. 560 00:30:28,600 --> 00:30:30,233 ANDREW TANENTZAP: Another major change 561 00:30:30,266 --> 00:30:31,866 {\an1}that we're seeing happening around lakes 562 00:30:31,900 --> 00:30:36,033 {\an1}is that cattails are moving northwards into the lakes 563 00:30:36,066 --> 00:30:38,700 {\an1}where they previously didn't grow. 564 00:30:38,733 --> 00:30:41,900 And where we compared the effect of cattails 565 00:30:41,933 --> 00:30:44,400 {\an1}versus pines and oaks and maples 566 00:30:44,433 --> 00:30:49,000 {\an1}on the amount of methane released from lake sediments... 567 00:30:49,966 --> 00:30:51,133 ..what we found was 568 00:30:51,166 --> 00:30:54,300 {\an1}that there was at least 400 times more methane produced 569 00:30:54,333 --> 00:30:56,866 when we added the cattail litter 570 00:30:56,900 --> 00:30:59,666 {\an1}than any of the tree litter. 571 00:30:59,700 --> 00:31:02,100 {\an8}NARRATOR: Models show that in the next 50 years, 572 00:31:02,133 --> 00:31:04,366 {\an7}cattails around lakes will double 573 00:31:04,400 --> 00:31:07,300 {\an7}and since more cattails means more methane, 574 00:31:07,333 --> 00:31:11,400 {\an7}methane production is predicted to increase by 70% 575 00:31:11,433 --> 00:31:14,166 {\an7}across all northern lakes. 576 00:31:14,200 --> 00:31:17,366 {\an1}From the global climate perspective, this is something 577 00:31:17,400 --> 00:31:19,866 that we really need to be worrying about 578 00:31:19,900 --> 00:31:23,033 {\an1}and thinking about how to actually mitigate 579 00:31:23,066 --> 00:31:25,900 {\an1}and offset these processes. 580 00:31:28,033 --> 00:31:29,300 {\an1}NARRATOR: At Earth's poles, 581 00:31:29,333 --> 00:31:32,933 {\an1}snow and ice reflect up to 85% of the sun's rays 582 00:31:32,966 --> 00:31:35,800 {\an1}away from the surface and back into space, 583 00:31:35,833 --> 00:31:38,566 {\an1}helping to keep the planet from becoming too hot. 584 00:31:39,666 --> 00:31:42,466 Today, that equilibrium is at risk 585 00:31:42,500 --> 00:31:45,066 {\an1}as one of the most important cooling mechanisms, 586 00:31:45,100 --> 00:31:49,533 {\an1}the albedo effect or Earth's reflectivity, is threatened. 587 00:31:51,666 --> 00:31:53,033 {\an1}Over the past few decades, 588 00:31:53,066 --> 00:31:56,566 {\an1}this natural mirror has begun to break down 589 00:31:56,600 --> 00:31:59,533 {\an1}as fossil fuel emissions raise temperatures, 590 00:31:59,566 --> 00:32:01,900 {\an1}melt snow and ice cover 591 00:32:01,933 --> 00:32:04,300 and reduce the planet's albedo. 592 00:32:06,966 --> 00:32:10,266 {\an1}As the planet loses its ability to reflect sunlight, 593 00:32:10,300 --> 00:32:13,666 a dangerous warming feedback loop is triggered. 594 00:32:18,200 --> 00:32:20,966 {\an1}The most alarming change is happening in the far north 595 00:32:21,000 --> 00:32:23,866 {\an1}where the temperature rise is causing the snow cover 596 00:32:23,900 --> 00:32:26,500 and sea ice to rapidly disappear. 597 00:32:29,300 --> 00:32:31,966 Don Perovich is a sea ice geophysicist 598 00:32:32,000 --> 00:32:33,600 {\an1}at Dartmouth College. 599 00:32:33,633 --> 00:32:34,800 {\an1}For the past 30 years, 600 00:32:34,833 --> 00:32:37,633 he's been documenting big changes in the Arctic. 601 00:32:37,666 --> 00:32:40,666 {\an1}DON PEROVICH: There's always been this annual cycle. 602 00:32:40,700 --> 00:32:44,933 {\an7}The ice grows usually, say, for nine or ten months of the year, 603 00:32:44,966 --> 00:32:46,866 {\an8}then melts for a couple of months. 604 00:32:46,900 --> 00:32:50,700 What's changing now is the timing. 605 00:32:51,533 --> 00:32:53,566 The melting is starting earlier, 606 00:32:53,600 --> 00:32:55,600 {\an1}the freezing is starting later. 607 00:32:57,033 --> 00:33:00,433 {\an1}We have much less coverage every month of the year, 608 00:33:00,466 --> 00:33:02,733 {\an1}particularly at the end of summer. 609 00:33:05,366 --> 00:33:07,866 {\an1}NARRATOR: Global warming from human-caused emissions 610 00:33:07,900 --> 00:33:09,266 {\an1}of heat-trapping gases, 611 00:33:09,300 --> 00:33:13,000 {\an1}carbon dioxide, methane, nitrous oxide and others, 612 00:33:13,033 --> 00:33:15,100 {\an1}is increasing the temperature in the Arctic 613 00:33:15,133 --> 00:33:18,033 {\an1}two to three times faster than the rest of the planet. 614 00:33:19,466 --> 00:33:22,966 {\an1}But that warming is then amplified by the loss of albedo 615 00:33:23,000 --> 00:33:25,966 {\an1}as the reflective ice and snow disappear. 616 00:33:28,533 --> 00:33:30,300 {\an1}DON PEROVICH: Say it's April 617 00:33:30,333 --> 00:33:32,233 and we're flying above the Arctic 618 00:33:32,266 --> 00:33:34,666 and we look down at the sea ice cover. 619 00:33:34,700 --> 00:33:38,366 {\an1}It's covered by snow, it's bright and it's white. 620 00:33:38,400 --> 00:33:41,466 Now, summer comes, that snow melts. 621 00:33:41,500 --> 00:33:43,700 {\an1}You get more open ocean. 622 00:33:43,733 --> 00:33:46,166 You're absorbing much more heat. 623 00:33:46,200 --> 00:33:48,333 {\an1}Instead of reflecting 85%, 624 00:33:48,366 --> 00:33:50,600 {\an1}you're absorbing 90%. 625 00:33:50,633 --> 00:33:55,366 {\an1}And so you're replacing one of the best natural reflectors, 626 00:33:55,400 --> 00:33:56,566 snow, 627 00:33:56,600 --> 00:33:59,700 {\an1}with one of the worst, the open ocean. 628 00:34:02,566 --> 00:34:04,833 {\an7}NARRATOR: Now, instead of reflecting the sunlight, 629 00:34:04,866 --> 00:34:06,700 {\an7}the ocean absorbs it, 630 00:34:06,733 --> 00:34:08,700 {\an7}heats up and melts more ice, 631 00:34:08,733 --> 00:34:10,300 {\an7}exposing more dark ocean 632 00:34:10,333 --> 00:34:12,133 {\an7}which absorbs more sunlight 633 00:34:12,166 --> 00:34:14,533 {\an7}in an amplifying cycle. 634 00:34:17,566 --> 00:34:20,700 GEORGE WOODWELL: As those darker waters warm, 635 00:34:20,733 --> 00:34:24,966 {\an1}they emit carbon dioxide and water vapor, 636 00:34:25,000 --> 00:34:27,300 {\an1}warming things further. 637 00:34:27,333 --> 00:34:29,266 {\an1}So, there are several aspects 638 00:34:29,300 --> 00:34:32,333 to this feedback in the Arctic problem 639 00:34:32,366 --> 00:34:36,433 {\an1}which are truly frightening. 640 00:34:36,466 --> 00:34:38,766 {\an1}NARRATOR: Scientists have been measuring Arctic sea ice 641 00:34:38,800 --> 00:34:40,966 {\an1}since long before satellites began taking 642 00:34:41,000 --> 00:34:44,033 {\an1}reliable measurements in the early 1970s. 643 00:34:45,833 --> 00:34:48,433 {\an1}By the end of that decade, the climate models predicted 644 00:34:48,466 --> 00:34:51,233 sea ice would begin to disappear with the increase 645 00:34:51,266 --> 00:34:54,233 {\an1}of heat-trapping gases in the atmosphere. 646 00:34:55,866 --> 00:34:58,166 Marika Holland is a climate modeler 647 00:34:58,200 --> 00:35:00,900 {\an1}from the National Center for Atmosphere Research. 648 00:35:02,933 --> 00:35:04,833 MARIKA HOLLAND: So, our first climate models 649 00:35:04,866 --> 00:35:07,466 {\an1}were developed in the 1970s. 650 00:35:07,500 --> 00:35:10,233 Those models, even in their simplicity, 651 00:35:10,266 --> 00:35:13,400 {\an8}predicted that with rising greenhouse gases 652 00:35:13,433 --> 00:35:14,733 {\an8}in the atmosphere, 653 00:35:14,766 --> 00:35:17,300 {\an8}we would see dramatic sea ice loss in the Arctic 654 00:35:17,333 --> 00:35:19,700 {\an1}and the Arctic warming would be amplified, 655 00:35:19,733 --> 00:35:22,033 {\an1}relative to the globe. 656 00:35:22,066 --> 00:35:24,266 {\an1}NARRATOR: And as measurement techniques improved, 657 00:35:24,300 --> 00:35:26,133 {\an1}scientists were alarmed to discover 658 00:35:26,166 --> 00:35:28,000 just how much ice had been lost. 659 00:35:29,100 --> 00:35:33,300 {\an7}The volume has decreased by 75% 660 00:35:33,333 --> 00:35:36,500 {\an8}in only 40 years. 661 00:35:36,533 --> 00:35:40,966 {\an1}It's just a breath-taking change in a very short time. 662 00:35:44,433 --> 00:35:45,833 {\an1}We call it the New Arctic now 663 00:35:45,866 --> 00:35:48,766 {\an1}because it's so different from what it used to be. 664 00:35:49,600 --> 00:35:51,900 The ice now is mainly consisting 665 00:35:51,933 --> 00:35:53,500 {\an1}of what we call first-year ice 666 00:35:53,533 --> 00:35:57,666 {\an1}which is just ice that's formed in that one winter. 667 00:35:57,700 --> 00:36:00,133 {\an1}And most of it doesn't survive through the summer. 668 00:36:00,166 --> 00:36:01,566 It all melts. 669 00:36:03,800 --> 00:36:05,933 {\an1}NARRATOR: Studies suggest that around a quarter 670 00:36:05,966 --> 00:36:09,366 {\an1}of global warming is caused by the loss of this sea ice. 671 00:36:11,033 --> 00:36:13,833 {\an1}And if you factor in the melting of snow cover 672 00:36:13,866 --> 00:36:15,533 {\an1}on the surrounding land, 673 00:36:15,566 --> 00:36:19,133 {\an1}together they account for an estimated 40% loss 674 00:36:19,166 --> 00:36:21,200 {\an1}in the planet's reflectivity. 675 00:36:23,033 --> 00:36:25,933 {\an1}MARIKA HOLLAND: The snow cover over land is very bright 676 00:36:25,966 --> 00:36:27,200 and very reflective. 677 00:36:27,233 --> 00:36:29,566 {\an1}It reflects an enormous amount of the sunlight 678 00:36:29,600 --> 00:36:33,100 {\an1}away from the surface, just like the sea ice cover does. 679 00:36:33,133 --> 00:36:35,166 {\an1}And we are seeing reductions 680 00:36:35,200 --> 00:36:38,500 {\an1}in the aerial coverage of snow over the land, 681 00:36:38,533 --> 00:36:40,533 {\an1}just like we're seeing reductions 682 00:36:40,566 --> 00:36:43,800 {\an1}in the aerial coverage of sea ice. 683 00:36:43,833 --> 00:36:46,266 {\an1}NARRATOR: With feedback loops amplifying the warming, 684 00:36:46,300 --> 00:36:51,266 {\an1}the landscape of the Arctic will change irrevocably. 685 00:36:51,300 --> 00:36:53,533 MARIKA HOLLAND: So, our climate model projections 686 00:36:53,566 --> 00:36:57,300 {\an1}suggest that we will lose the Arctic sea ice cover 687 00:36:57,333 --> 00:37:02,266 {\an1}in the summer months altogether by the end of this century. 688 00:37:03,500 --> 00:37:07,166 If we continue to increase greenhouse gases 689 00:37:07,200 --> 00:37:10,266 {\an1}in the atmosphere through the burning of fossil fuels, 690 00:37:10,300 --> 00:37:12,233 {\an1}we ultimately will get to a state 691 00:37:12,266 --> 00:37:14,833 where we lose the winter sea ice as well. 692 00:37:16,400 --> 00:37:18,133 NARRATOR: A sobering prediction, 693 00:37:18,166 --> 00:37:21,200 considering that ice has covered the Arctic Ocean 694 00:37:21,233 --> 00:37:24,066 {\an1}for more than two and a half million years. 695 00:37:26,600 --> 00:37:28,600 And the warming happening in the Arctic 696 00:37:28,633 --> 00:37:30,266 {\an1}isn't staying in the Arctic. 697 00:37:32,233 --> 00:37:35,066 {\an1}The air there is mixing into the global atmosphere 698 00:37:35,100 --> 00:37:36,466 elsewhere on Earth 699 00:37:36,500 --> 00:37:39,566 and raising global temperatures. 700 00:37:39,600 --> 00:37:42,000 {\an1}MARIKA HOLLAND: The Arctic plays a very central role 701 00:37:42,033 --> 00:37:43,366 in Earth's climate. 702 00:37:43,400 --> 00:37:47,533 Even if you just lose sea ice cover in the Arctic, 703 00:37:47,566 --> 00:37:50,733 the tropics will feel that enhanced warming. 704 00:37:52,233 --> 00:37:55,033 {\an1}NARRATOR: This means amplification of problems 705 00:37:55,066 --> 00:37:57,966 the climate crisis is already causing - 706 00:37:58,000 --> 00:37:59,566 crops suffering, 707 00:37:59,600 --> 00:38:01,700 {\an1}food prices going up... 708 00:38:02,666 --> 00:38:04,633 {\an1}..wet areas becoming wetter... 709 00:38:05,533 --> 00:38:07,500 {\an1}..dry areas becoming drier. 710 00:38:11,466 --> 00:38:15,000 {\an1}And as the climate warms, it kicks in another feedback loop, 711 00:38:15,033 --> 00:38:19,333 {\an1}set in motion by the melting of massive glacial ice sheets. 712 00:38:20,366 --> 00:38:22,566 {\an1}In the past 30 years, the loss of ice 713 00:38:22,600 --> 00:38:25,900 {\an1}on the Greenland ice sheet has increased six-fold, 714 00:38:25,933 --> 00:38:28,133 {\an1}leading to a rise in sea level. 715 00:38:30,266 --> 00:38:31,666 {\an8}As the ocean rises, 716 00:38:31,700 --> 00:38:35,300 {\an7}the higher, warmer water melts more land ice, 717 00:38:35,333 --> 00:38:37,200 {\an7}raising sea levels further 718 00:38:37,233 --> 00:38:39,033 {\an7}and melting even more ice 719 00:38:39,066 --> 00:38:40,566 {\an8}in a vicious cycle. 720 00:38:47,333 --> 00:38:48,800 In the South Pole, 721 00:38:48,833 --> 00:38:50,700 {\an1}the increased temperature is thawing 722 00:38:50,733 --> 00:38:53,133 the miles-thick Antarctic ice sheets 723 00:38:53,166 --> 00:38:55,033 {\an1}that have been accumulating on land 724 00:38:55,066 --> 00:38:57,666 {\an1}for over 40 million years. 725 00:38:59,733 --> 00:39:02,300 {\an1}MARIKA HOLLAND: Loss of ice over the Antarctic continent 726 00:39:02,333 --> 00:39:04,200 {\an1}doesn't have as much of an albedo feedback 727 00:39:04,233 --> 00:39:05,833 {\an1}because it's so thick, 728 00:39:05,866 --> 00:39:08,966 {\an1}but as that ice enters the ocean, 729 00:39:09,000 --> 00:39:10,900 {\an1}it causes sea level to rise. 730 00:39:12,500 --> 00:39:14,000 {\an1}NARRATOR: If both Greenland 731 00:39:14,033 --> 00:39:16,833 {\an1}and Antarctica's glacial ice shelves were to melt, 732 00:39:16,866 --> 00:39:21,333 {\an1}sea levels would potentially rise by more than 100 feet. 733 00:39:25,000 --> 00:39:27,633 {\an1}This resulting destruction to coastlines 734 00:39:27,666 --> 00:39:30,300 {\an1}would uproot millions of people around the world. 735 00:39:34,400 --> 00:39:35,533 It would also mean 736 00:39:35,566 --> 00:39:37,533 {\an1}the ice sheets would reach a tipping point, 737 00:39:37,566 --> 00:39:40,066 {\an1}taking thousands of years to recover. 738 00:39:43,966 --> 00:39:47,700 {\an1}So, if we lose an enormous amount of ice from the land, 739 00:39:47,733 --> 00:39:53,233 {\an1}re-establishing that is a very long timescale issue. 740 00:39:55,300 --> 00:39:57,433 {\an1}NARRATOR: And if we continue with business as usual, 741 00:39:57,466 --> 00:40:00,333 {\an1}the warming of the Arctic will cause the feedback loops 742 00:40:00,366 --> 00:40:03,700 at both poles to spin out of control. 743 00:40:05,333 --> 00:40:06,900 MARIKA HOLLAND: The models predict, 744 00:40:06,933 --> 00:40:09,200 if we continue on the path we're on, 745 00:40:09,233 --> 00:40:13,400 {\an1}that the Arctic will experience very dramatic changes 746 00:40:13,433 --> 00:40:15,800 {\an1}and that those changes will reverberate 747 00:40:15,833 --> 00:40:17,400 {\an1}throughout the system, 748 00:40:17,433 --> 00:40:18,900 the human system, 749 00:40:18,933 --> 00:40:20,533 {\an1}the biological system, 750 00:40:20,566 --> 00:40:22,666 {\an1}the socio-economic system. 751 00:40:30,766 --> 00:40:33,300 NARRATOR: White, puffy cumulus, 752 00:40:33,333 --> 00:40:36,200 {\an1}dark nimbus storm clouds, 753 00:40:36,233 --> 00:40:39,100 {\an1}wispy, thin cirrus clouds. 754 00:40:39,133 --> 00:40:41,266 {\an1}Not just beautiful to look at, 755 00:40:41,300 --> 00:40:44,733 {\an1}clouds play an important role in Earth's climate. 756 00:40:46,366 --> 00:40:48,166 {\an1}They're formed by water vapor, 757 00:40:48,200 --> 00:40:50,100 {\an1}a naturally occurring gas created 758 00:40:50,133 --> 00:40:53,300 when water evaporates from lakes and oceans. 759 00:40:54,366 --> 00:40:57,366 Water vapor is also a heat-trapping gas. 760 00:40:57,400 --> 00:40:59,233 It's part of a dangerous feedback loop 761 00:40:59,266 --> 00:41:02,833 {\an1}that's heating the Earth beyond its natural limits, 762 00:41:02,866 --> 00:41:05,666 {\an1}accounting for about 60% of all global warming 763 00:41:05,700 --> 00:41:08,933 {\an1}caused by heat-trapping gases in the atmosphere. 764 00:41:10,533 --> 00:41:13,266 {\an1}As fossil fuel emissions raise temperatures, 765 00:41:13,300 --> 00:41:16,233 {\an1}the atmosphere absorbs more water vapor 766 00:41:16,266 --> 00:41:17,800 {\an1}which then traps more heat, 767 00:41:17,833 --> 00:41:19,300 {\an1}warming the planet further 768 00:41:19,333 --> 00:41:21,833 {\an1}in an ever-amplifying loop. 769 00:41:23,200 --> 00:41:25,466 In fact, the water vapor feedback 770 00:41:25,500 --> 00:41:28,666 {\an1}amplifies global warming from human activity 771 00:41:28,700 --> 00:41:30,766 {\an1}between two and three times. 772 00:41:33,400 --> 00:41:36,300 {\an1}For the past 30 years, Jennifer Francis has been studying 773 00:41:36,333 --> 00:41:41,133 {\an1}how increased greenhouses gases affect the atmosphere. 774 00:41:41,166 --> 00:41:43,933 JENNIFER FRANCIS: Water vapor is just water 775 00:41:43,966 --> 00:41:46,133 in a gaseous form. 776 00:41:46,166 --> 00:41:47,800 {\an1}When you take a pot of water 777 00:41:47,833 --> 00:41:50,033 {\an1}and put it on your stove and boil it, 778 00:41:50,066 --> 00:41:52,766 {\an1}you see steam which is still in the liquid form, 779 00:41:52,800 --> 00:41:54,300 {\an1}but then it disappears 780 00:41:54,333 --> 00:41:57,266 {\an1}and it goes into the atmosphere and it's completely invisible. 781 00:41:57,300 --> 00:41:59,666 {\an1}So, the same kind of thing is happening 782 00:41:59,700 --> 00:42:00,966 {\an1}in the climate system 783 00:42:01,000 --> 00:42:04,566 {\an1}where as we warm the air and we warm the oceans, 784 00:42:04,600 --> 00:42:07,433 {\an1}more evaporation is occurring from the oceans 785 00:42:07,466 --> 00:42:10,666 {\an1}and putting more water vapor in the atmosphere. 786 00:42:11,933 --> 00:42:14,066 {\an1}NARRATOR: While some of this stays in the atmosphere 787 00:42:14,100 --> 00:42:15,966 {\an1}and traps heat in gaseous form, 788 00:42:16,000 --> 00:42:17,933 {\an1}some of it cools and condenses, 789 00:42:17,966 --> 00:42:22,933 {\an1}forming clouds which can both heat and cool the planet. 790 00:42:22,966 --> 00:42:25,166 We still don't have good mechanisms, 791 00:42:25,200 --> 00:42:27,133 {\an7}as good as we would like, 792 00:42:27,166 --> 00:42:30,633 {\an7}for cloud feedbacks... 793 00:42:30,666 --> 00:42:32,566 ..because clouds are very complicated. 794 00:42:34,666 --> 00:42:36,733 {\an1}NARRATOR: Clouds can lower the temperature 795 00:42:36,766 --> 00:42:39,066 {\an1}because their white color reflects sunlight 796 00:42:39,100 --> 00:42:40,433 back into space, 797 00:42:40,466 --> 00:42:43,200 cooling the Earth like on a hot, sunny day 798 00:42:43,233 --> 00:42:46,700 {\an1}when clouds offer relief from the heat. 799 00:42:46,733 --> 00:42:49,366 {\an1}Conversely, clouds can trap heat below them, 800 00:42:49,400 --> 00:42:51,366 {\an1}heating Earth's surface 801 00:42:51,400 --> 00:42:53,266 {\an1}like when it's warmer on a cloudy night 802 00:42:53,300 --> 00:42:55,533 than on a clear one. 803 00:42:55,566 --> 00:42:57,500 {\an1}Scientists conclude that, on balance, 804 00:42:57,533 --> 00:42:59,866 {\an1}clouds raise the temperature. 805 00:43:01,833 --> 00:43:05,600 {\an7}And as the climate warms, the oceans are also heating up, 806 00:43:05,633 --> 00:43:07,833 {\an7}causing increased evaporation, 807 00:43:07,866 --> 00:43:09,666 {\an7}creating even more water vapor, 808 00:43:09,700 --> 00:43:11,233 {\an8}trapping more heat, 809 00:43:11,266 --> 00:43:13,333 {\an7}leading to more evaporation 810 00:43:13,366 --> 00:43:16,533 {\an8}and becoming another amplifying loop. 811 00:43:18,866 --> 00:43:21,666 It's this combination of increased water vapor 812 00:43:21,700 --> 00:43:25,266 {\an1}and the warming of the oceans that's driving hurricanes. 813 00:43:37,400 --> 00:43:39,000 KERRY EMANUEL: More than 30 years ago, 814 00:43:39,033 --> 00:43:41,933 we predicted that global warming would result 815 00:43:41,966 --> 00:43:43,566 {\an1}in more intense storms, 816 00:43:43,600 --> 00:43:45,266 and we're beginning to see that, 817 00:43:45,300 --> 00:43:47,800 {\an8}even in places like Florida and the Bahamas 818 00:43:47,833 --> 00:43:50,766 {\an8}which are adapted to hurricanes. 819 00:43:50,800 --> 00:43:52,166 {\an7}They're adapted up to a point 820 00:43:52,200 --> 00:43:55,666 {\an1}and when we begin to see stronger storms like Dorian, 821 00:43:55,700 --> 00:43:58,200 that adaptation doesn't mean anything. 822 00:44:05,166 --> 00:44:06,833 NARRATOR: In addition to water vapor, 823 00:44:06,866 --> 00:44:08,666 another atmospheric feedback loop 824 00:44:08,700 --> 00:44:11,133 {\an1}is creating extreme weather, 825 00:44:11,166 --> 00:44:14,266 this one involving the jet stream. 826 00:44:14,300 --> 00:44:17,633 {\an1}JENNIFER FRANCIS: The jet stream is this river of wind 827 00:44:17,666 --> 00:44:20,233 high over our heads, up where the jets fly, 828 00:44:20,266 --> 00:44:22,866 that encircles the Northern Hemisphere 829 00:44:22,900 --> 00:44:24,633 and that jet stream is responsible 830 00:44:24,666 --> 00:44:26,933 for creating pretty much all the weather 831 00:44:26,966 --> 00:44:29,900 that we experience in this part of the world. 832 00:44:32,800 --> 00:44:35,700 {\an1}NARRATOR: To illustrate, imagine a layer of air 833 00:44:35,733 --> 00:44:39,333 {\an1}extending from the warm south to the cold north. 834 00:44:42,500 --> 00:44:44,200 Warm air expands, 835 00:44:44,233 --> 00:44:47,333 {\an1}so the layer over the south rises up higher 836 00:44:47,366 --> 00:44:49,166 {\an1}than the air over the north. 837 00:44:52,033 --> 00:44:56,233 {\an1}Because of gravity, the warm air higher up flows downhill, 838 00:44:56,266 --> 00:44:58,833 {\an1}just like water flows down a mountain. 839 00:45:00,666 --> 00:45:04,900 {\an1}This downward movement creates a south-to-north wind. 840 00:45:06,100 --> 00:45:07,933 {\an1}But because the Earth is spinning, 841 00:45:07,966 --> 00:45:10,833 {\an1}this wind gets turned to the east 842 00:45:10,866 --> 00:45:14,533 and becomes a west-to-east flow of wind. 843 00:45:14,566 --> 00:45:16,833 {\an1}That's the jet stream. 844 00:45:16,866 --> 00:45:18,600 The greater the temperature difference 845 00:45:18,633 --> 00:45:21,200 between the north and south air masses, 846 00:45:21,233 --> 00:45:24,666 {\an1}the faster and stronger the jet stream winds blow. 847 00:45:24,700 --> 00:45:27,333 Historically, Arctic air has been much colder 848 00:45:27,366 --> 00:45:29,000 {\an1}than the air to the south, 849 00:45:29,033 --> 00:45:31,366 {\an1}keeping the jet stream fairly straight 850 00:45:31,400 --> 00:45:34,966 {\an1}with relatively small north-south meanders. 851 00:45:35,000 --> 00:45:36,700 {\an1}But with the Arctic warming 852 00:45:36,733 --> 00:45:39,800 {\an1}at two to three times the rate as the rest of the globe, 853 00:45:39,833 --> 00:45:43,200 {\an1}that temperature differential has decreased. 854 00:45:43,233 --> 00:45:45,033 This weakens the jet stream winds, 855 00:45:45,066 --> 00:45:49,900 {\an1}causing them to take larger swings north and south... 856 00:45:49,933 --> 00:45:52,200 ..which, in turn, impacts the weather. 857 00:45:53,233 --> 00:45:55,300 JENNIFER FRANCIS: This is the feedback loop. 858 00:45:55,333 --> 00:45:56,966 {\an7}We're warming the Arctic, 859 00:45:57,000 --> 00:45:59,233 {\an7}we're reducing the winds of the jet stream, 860 00:45:59,266 --> 00:46:02,333 {\an1}we're seeing it take these bigger north-south swings 861 00:46:02,366 --> 00:46:05,033 which then transfers even more heat 862 00:46:05,066 --> 00:46:07,500 {\an1}from the south to the north into the Arctic 863 00:46:07,533 --> 00:46:09,000 {\an1}which makes it even warmer, 864 00:46:09,033 --> 00:46:10,533 {\an1}which weakens the winds more 865 00:46:10,566 --> 00:46:13,166 and it sets up this vicious cycle. 866 00:46:16,666 --> 00:46:19,800 {\an1}NARRATOR: Recent examples are the multi-year drought 867 00:46:19,833 --> 00:46:21,200 in the western US 868 00:46:21,233 --> 00:46:23,466 {\an1}and the increase in wildfires. 869 00:46:23,500 --> 00:46:27,366 They're connected to a larger north-south swing 870 00:46:27,400 --> 00:46:29,066 in the jet stream. 871 00:46:33,266 --> 00:46:35,900 {\an1}We're now living in a world where extreme weather events 872 00:46:35,933 --> 00:46:38,700 {\an1}like these are the norm, not the exception. 873 00:46:49,933 --> 00:46:52,266 {\an1}Even if we could staunch the emissions 874 00:46:52,300 --> 00:46:54,200 {\an1}of greenhouse gases today, 875 00:46:54,233 --> 00:46:56,833 {\an1}these weather patterns may continue 876 00:46:56,866 --> 00:46:59,266 {\an1}for a long time to come. 877 00:46:59,300 --> 00:47:00,966 JENNIFER FRANCIS: So, the wet places 878 00:47:01,000 --> 00:47:02,633 are going to tend to get wetter. 879 00:47:02,666 --> 00:47:06,366 On the other hand, places that are already dry, 880 00:47:06,400 --> 00:47:09,200 {\an1}they're also going to see more evaporation 881 00:47:09,233 --> 00:47:12,000 because of the air being warmer. 882 00:47:13,566 --> 00:47:17,133 {\an7}Where we are now, it's like driving in a car in a dense fog 883 00:47:17,166 --> 00:47:19,800 {\an7}and you know there's a cliff out there somewhere, 884 00:47:19,833 --> 00:47:21,266 {\an1}but you don't know where. 885 00:47:21,300 --> 00:47:22,809 {\an1}Do you want to be going 60 miles an hour 886 00:47:22,833 --> 00:47:24,833 {\an1}or should you be going about ten miles an hour? 887 00:47:28,333 --> 00:47:30,066 NARRATOR: Today, we have a choice. 888 00:47:30,100 --> 00:47:32,733 If we take our foot off the accelerator, 889 00:47:32,766 --> 00:47:35,266 we can reverse the feedback loops 890 00:47:35,300 --> 00:47:37,266 {\an1}and begin to cool the planet. 891 00:47:45,900 --> 00:47:49,300 If we don't deal with this climate change issue... 892 00:47:50,200 --> 00:47:52,400 ..we're going to be in deep trouble. 893 00:47:55,833 --> 00:47:59,200 {\an1}KERRY EMANUEL: The emission of greenhouse gases is an example 894 00:47:59,233 --> 00:48:01,300 of a market failure, 895 00:48:01,333 --> 00:48:04,866 {\an1}one business enterprise passing on the real cost 896 00:48:04,900 --> 00:48:09,266 {\an1}of doing business to people who aren't party to that business, 897 00:48:09,300 --> 00:48:11,533 that is, most of the rest of us. 898 00:48:15,500 --> 00:48:18,266 {\an1}NARRATOR: George Woodwell was an early pioneer, 899 00:48:18,300 --> 00:48:20,733 {\an1}warning about fossil fuel use 900 00:48:20,766 --> 00:48:24,800 {\an1}setting off warming feedback loops five decades ago. 901 00:48:24,833 --> 00:48:27,300 He's convinced the solution lies 902 00:48:27,333 --> 00:48:30,600 {\an1}with nature's own ability to cool the planet. 903 00:48:32,933 --> 00:48:37,500 GEORGE WOODWELL: We can store carbon in life. 904 00:48:37,533 --> 00:48:40,933 {\an1}If we want to be optimistic, we have to be very progressive 905 00:48:40,966 --> 00:48:45,333 in our transition away from fossil fuels 906 00:48:45,366 --> 00:48:48,233 {\an1}and into a new green world. 907 00:49:06,866 --> 00:49:10,233 {\an1}NARRATOR: With every country contributing to the problem, 908 00:49:10,266 --> 00:49:13,533 {\an1}each now needs to be part of the solution. 909 00:49:13,566 --> 00:49:16,633 {\an1}GEORGE WOODWELL: And that requires managing the world 910 00:49:16,666 --> 00:49:20,933 {\an1}in such a way that we do not exploit carbon compounds 911 00:49:20,966 --> 00:49:23,533 and dump the waste into the atmosphere. 912 00:49:24,766 --> 00:49:26,566 NARRATOR: In every sector of the economy, 913 00:49:26,600 --> 00:49:28,300 {\an1}we have the technology and knowledge 914 00:49:28,333 --> 00:49:30,266 to move towards sources of energy 915 00:49:30,300 --> 00:49:33,400 that do not produce heat-trapping gases. 916 00:49:33,433 --> 00:49:35,433 {\an1}What we need is the will. 917 00:49:38,166 --> 00:49:40,000 KERRY EMANUEL: I'm encouraged by the fact 918 00:49:40,033 --> 00:49:43,066 that other countries have decarbonized 919 00:49:43,100 --> 00:49:47,100 {\an1}their electricity sector in ten to twelve years, 920 00:49:47,133 --> 00:49:49,133 {\an1}so I know we can do it 921 00:49:49,166 --> 00:49:50,666 {\an1}and those countries that did it 922 00:49:50,700 --> 00:49:53,000 {\an1}grew their economies rapidly while doing it. 923 00:49:53,033 --> 00:49:57,633 But we have to put the incentives in place. 924 00:49:57,666 --> 00:49:58,833 (CHANTING) 925 00:49:58,866 --> 00:50:01,700 {\an1}The most important thing citizens can do 926 00:50:01,733 --> 00:50:03,766 {\an1}is to educate themselves on this issue 927 00:50:03,800 --> 00:50:07,966 {\an1}and vote for politicians who take this problem seriously 928 00:50:08,000 --> 00:50:10,700 and have good ideas for how to solve it. 929 00:50:11,766 --> 00:50:14,133 {\an1}SUE NATALI: Communicating with our policy-makers 930 00:50:14,166 --> 00:50:15,500 {\an1}that this is important to us, 931 00:50:15,533 --> 00:50:17,233 {\an1}that this is impacting each one of us, 932 00:50:17,266 --> 00:50:18,566 {\an1}that this is important 933 00:50:18,600 --> 00:50:21,533 for human health, for human well-being, 934 00:50:21,566 --> 00:50:25,533 {\an7}is the most important action that each one of us can take. 935 00:50:25,566 --> 00:50:28,566 {\an1}PHILIP DUFFY: To successfully address climate change requires 936 00:50:28,600 --> 00:50:31,166 {\an1}an unprecedented level of societal cooperation, 937 00:50:31,200 --> 00:50:34,633 {\an7}cooperation across nations, cooperation within nations, 938 00:50:34,666 --> 00:50:36,766 {\an7}across multiple sectors. 939 00:50:36,800 --> 00:50:38,833 NARRATOR: Today, we have a choice. 940 00:50:38,866 --> 00:50:42,100 We can continue with business as usual 941 00:50:42,133 --> 00:50:45,600 {\an1}and let these warming feedback loops spin out of control 942 00:50:45,633 --> 00:50:48,133 or we can choose another way of living 943 00:50:48,166 --> 00:50:52,166 {\an1}and implement policies that support a sustainable future, 944 00:50:52,200 --> 00:50:53,300 but we need leaders 945 00:50:53,333 --> 00:50:56,100 {\an1}who understand the urgency of getting it done 946 00:50:56,133 --> 00:51:00,200 {\an1}and an energized public to advocate for change. 947 00:51:00,233 --> 00:51:02,366 {\an7}(GRETA THUNBERG SPEAKING) 948 00:51:14,766 --> 00:51:17,333 {\an8}We, the people. 949 00:51:18,366 --> 00:51:19,500 {\an8}Thank you. 950 00:51:47,566 --> 00:51:49,600 Most people I know, I encounter, 951 00:51:49,633 --> 00:51:55,333 {\an1}haven't even heard of feedback loops or tipping points, 952 00:51:55,366 --> 00:51:57,500 {\an1}chain reactions and so on. 953 00:51:58,433 --> 00:51:59,500 {\an1}But they are so crucial 954 00:51:59,533 --> 00:52:02,400 to understanding how the world works. 955 00:52:02,433 --> 00:52:06,733 We have... we have such a lack of respect 956 00:52:06,766 --> 00:52:08,800 for nature and for the environment 957 00:52:08,833 --> 00:52:12,000 {\an1}that we just think that things will work out in the end. 958 00:52:12,033 --> 00:52:14,166 We cannot solve the climate emergency 959 00:52:14,200 --> 00:52:17,566 {\an1}without taking these feedback loops into account 960 00:52:17,600 --> 00:52:19,933 and without really understanding them, 961 00:52:19,966 --> 00:52:22,000 {\an1}so that is a crucial step.