WEBVTT FILE 1 00:00:00.001 --> 00:00:03.449 [MUSIC] 2 00:00:03.449 --> 00:00:04.911 This is a story about heat. 3 00:00:06.934 --> 00:00:10.275 Heat in our atmosphere, oceans, and land. 4 00:00:10.750 --> 00:00:15.519 When you think about it, events like drought, hurricanes, fires - all of those are just 5 00:00:15.519 --> 00:00:19.720 different ways we see heat expressed throughout the Earth’s system. 6 00:00:24.610 --> 00:00:28.680 You’ve probably been bombarded with a lot of intense headlines in 2020. 7 00:00:28.680 --> 00:00:32.720 “Hottest temperature recorded here, largest wildfires there..” 8 00:00:34.584 --> 00:00:37.520 It’s been a lot to take in. 9 00:00:37.520 --> 00:00:42.079 My name is Lesley Ott and I am a research meteorologist at NASA’s Goddard Space Flight Center 10 00:00:42.340 --> 00:00:45.470 So, the reality is the stage was set many years ago for these events. 11 00:00:46.349 --> 00:00:50.280 Over the last century, human activities have increased the concentration of greenhouse 12 00:00:50.280 --> 00:00:51.550 gases in our atmosphere. 13 00:00:51.690 --> 00:00:56.646 These gasses act like a blanket, trapping heat and leading to overall warming of the planet. 14 00:00:56.921 --> 00:01:00.326 Many of these gases remain in the atmosphere for a long time, meaning that we’ll be feeling 15 00:01:00.326 --> 00:01:04.100 the consequences of this trapped heat for many years to come. 16 00:01:04.100 --> 00:01:08.819 Which, unfortunately, means next year is probably going to bring a lot of the same kinds 17 00:01:08.819 --> 00:01:12.289 of stories that we saw in 2020. 18 00:01:12.289 --> 00:01:15.729 But taking a look at all the different ways our planet responds to the variations and 19 00:01:15.729 --> 00:01:19.981 movement of heat can help us better prepare for the future. 20 00:01:25.733 --> 00:01:30.702 Maybe one of the most obvious ways we saw heat this year was through fire. 21 00:01:33.305 --> 00:01:35.990 I know the Australian bush fires were big news last January. 22 00:01:35.990 --> 00:01:40.329 And, when you think about it, years of prolonged hot temperatures and drought really set the 23 00:01:40.329 --> 00:01:44.002 stage for these fires to be more likely and more severe. 24 00:01:45.938 --> 00:01:49.948 With drought and heat waves, we typically see an increase in the availability of dry 25 00:01:49.948 --> 00:01:52.389 fuels, which leads to more powerful fires. 26 00:01:52.389 --> 00:01:56.939 So when you have multiple years of intense heat, it’s not surprising to have significant 27 00:01:56.939 --> 00:01:59.469 fire events like we saw in Australia. 28 00:01:59.469 --> 00:02:04.539 These fires were so extreme, that we saw smoke injected as high as 18 miles above the surface 29 00:02:04.539 --> 00:02:09.369 - that’s really important because when smoke is injected that high, it can have the same 30 00:02:09.369 --> 00:02:14.480 type of effect as a volcano, having these very very broad impacts across whole hemispheres 31 00:02:14.480 --> 00:02:15.828 of the planet. 32 00:02:17.834 --> 00:02:22.384 At NASA, we use computer models like the Goddard Earth Observing System to help us study how 33 00:02:22.384 --> 00:02:25.360 aerosols and particulate matter move through the atmosphere. 34 00:02:25.360 --> 00:02:30.780 So we take these models and input real-world observations and data to track fire emissions 35 00:02:30.780 --> 00:02:35.030 to help understand how they are forming, where they are going, and how much of an impact 36 00:02:35.030 --> 00:02:37.280 they will have on you and me. 37 00:02:46.313 --> 00:02:52.523 In California, heat waves have increased fire risk, and as a result, we saw a lot of synchronized 38 00:02:52.523 --> 00:02:56.239 fire activity, that is, many dangerous wildfires burning at the same time. 39 00:02:58.095 --> 00:03:02.750 And unfortunately, these types of huge fire events are becoming more and more common across 40 00:03:02.750 --> 00:03:04.341 the western United States. 41 00:03:04.481 --> 00:03:06.826 And that’s a big problem. 42 00:03:11.543 --> 00:03:15.053 This year, Siberia also had a remarkable and active fire season. 43 00:03:15.510 --> 00:03:20.090 What we saw was that temperatures in the region were much higher than normal for this time 44 00:03:20.090 --> 00:03:21.640 of year. 45 00:03:21.640 --> 00:03:25.510 In fact, the temperatures above the Arctic Circle broke records in many of the same regions 46 00:03:25.510 --> 00:03:27.565 where fires were burning actively. 47 00:03:29.342 --> 00:03:33.665 In the Arctic and boreal forest ecosystems, heat waves can exacerbate fires. 48 00:03:34.878 --> 00:03:38.890 And in the Arctic you also have to factor in permafrost, which is soil that's 49 00:03:38.890 --> 00:03:43.430 frozen for long periods of time, and that can make the impact of fires in high latitudes 50 00:03:43.430 --> 00:03:44.706 even more complex. 51 00:03:45.972 --> 00:03:51.287 When severe fires burn in areas with permafrost, we lose this important insulating organic 52 00:03:51.287 --> 00:03:55.720 soil layer, which accelerates thawing, and its potentially releasing carbon that’s 53 00:03:55.720 --> 00:04:00.370 been stored in the soil for hundreds and in some cases, even thousands of years. 54 00:04:02.322 --> 00:04:06.650 And then you sometimes see these ‘zombie fires’, which happen when wildfires burn 55 00:04:06.650 --> 00:04:10.150 in deep peatlands or smolder in forests under snowfall. 56 00:04:10.150 --> 00:04:14.430 If that temperature doesn't get cold enough to extinguish the fire, they can continue 57 00:04:14.430 --> 00:04:19.400 to burn over the winter even long after the visible fires have been extinguished at the surface. 58 00:04:20.259 --> 00:04:24.735 So come spring, they reemerge and they continue to burn back on the surface again. 59 00:04:28.253 --> 00:04:31.890 Studying what happens in the Arctic is really important because it’s warming about three 60 00:04:31.890 --> 00:04:33.810 times faster than the rest of the planet. 61 00:04:33.810 --> 00:04:38.560 And all those aerosols and carbon that come out of the Arctic doesn't necessarily stay 62 00:04:38.560 --> 00:04:43.381 there, they affect the heating and air pollution in much larger regions of the planet. 63 00:04:53.707 --> 00:04:57.510 Another part of the planet affected by heat, of course, is ice. 64 00:04:57.510 --> 00:05:01.200 Land ice in the form of ice sheets and glaciers, where we’ve seen significant melt in recent 65 00:05:01.200 --> 00:05:04.385 decades, and frozen ocean water, or sea ice. 66 00:05:06.000 --> 00:05:09.810 This year, the Arctic sea ice minimum almost reached a new record low. 67 00:05:09.810 --> 00:05:13.890 It was second only to 2012’s extent -- which was an anomalously low year in part due to 68 00:05:13.890 --> 00:05:15.150 unusual weather conditions. 69 00:05:16.029 --> 00:05:18.510 Sea ice shrinks and grows with the seasons. 70 00:05:18.510 --> 00:05:22.760 After reaching an annual minimum extent in September, Arctic sea ice begins to grow again 71 00:05:22.760 --> 00:05:24.950 as sea temperatures cool off for the winter. 72 00:05:24.950 --> 00:05:29.373 This year, Arctic sea ice had an unusually slow start to the regrowth period. 73 00:05:30.270 --> 00:05:33.470 In particular, the Laptev Sea, which is called sometimes called a sea ice nursery 74 00:05:33.470 --> 00:05:37.530 because much of the Arctic sea ice initially forms there, was too warm for meaningful 75 00:05:37.530 --> 00:05:40.501 sea ice growth until much later in the season than usual. 76 00:05:48.000 --> 00:05:53.370 Oceans absorb heat from the sun and our atmosphere prevents this heat from escaping back to space. 77 00:05:53.370 --> 00:05:58.158 The movement of this heat is one of the primary drivers of circulation and global weather patterns. 78 00:05:59.721 --> 00:06:03.540 We can measure the temperature of the ocean and what we saw this year was unusually high 79 00:06:03.540 --> 00:06:06.590 surface temperatures across the Atlantic. 80 00:06:06.590 --> 00:06:09.990 The warm moisture that comes off of the ocean acts as fuel to storms. 81 00:06:09.990 --> 00:06:14.860 So, as this layer of the ocean gets even warmer, we’re seeing that storms are becoming more 82 00:06:14.860 --> 00:06:17.090 and more intense over time. 83 00:06:18.000 --> 00:06:24.190 In fact, 2020's sea surface temperature contributed to an exceptional year in terms of Atlantic hurricanes. 84 00:06:24.190 --> 00:06:30.122 We saw 30 named storms - a new record, and 12 of these storms made landfall in the US. 85 00:06:34.572 --> 00:06:39.239 What’s really interesting is that many of these storms intensified really really rapidly. 86 00:06:42.300 --> 00:06:46.180 Not only are storms intensifying more quickly, but what we’re also seeing is that they 87 00:06:46.180 --> 00:06:51.437 are stalling near coastal regions more often, which is devastating in terms of floods and storm surge. 88 00:06:57.974 --> 00:07:02.900 While we’re not 100% sure what is causing these storms to stall, it may have to do with 89 00:07:02.900 --> 00:07:06.571 climate patterns shifting in response to rising global temperatures. 90 00:07:11.057 --> 00:07:15.090 It’s always really tough for a scientist to say any particular fire or any particular 91 00:07:15.090 --> 00:07:16.890 event was because of climate change. 92 00:07:16.890 --> 00:07:21.730 But we’re getting to a point where we’re starting to see season after season of record-breaking 93 00:07:21.730 --> 00:07:27.480 wildfire, season after season of really intense storms, that it becomes much easier to understand 94 00:07:27.480 --> 00:07:30.890 that this is likely the result of long-term climate change. 95 00:07:32.033 --> 00:07:35.340 In general, more heat means more energy in the Earth system. 96 00:07:35.340 --> 00:07:40.060 So, while 2020 was a significant year, it’s important to know that this probably wasn’t 97 00:07:40.060 --> 00:07:41.510 an anomaly of a year. 98 00:07:41.510 --> 00:07:45.810 We’re likely to experience many similar years as the Earth’s climate gets warmer. 99 00:07:46.866 --> 00:07:51.723 So, while we saw a small dip in emissions this year due to COVID shutdowns, it was pretty short-lived. 100 00:07:52.120 --> 00:07:55.920 The vast majority of our greenhouse gas emissions come from things like electricity generation, 101 00:07:55.920 --> 00:07:59.769 which were less affected by the shutdowns than emissions from cars and airplanes. 102 00:08:01.159 --> 00:08:05.460 But we know that human activities have a powerful impact on our environment. 103 00:08:05.460 --> 00:08:09.330 Long term strategies to curb human-induced climate change would have to focus on implementing 104 00:08:09.330 --> 00:08:14.117 cleaner technologies so we can reduce emissions without affecting people’s daily lives. 105 00:08:16.313 --> 00:08:18.973 So while this is a story about heat, it is also a story about connections. 106 00:08:18.973 --> 00:08:21.610 Nothing on our planet happens in a vacuum, and our actions today impact our tomorrow. 107 00:08:21.751 --> 00:08:23.908 The choices we make now can make the difference between continued increases in greenhouse 108 00:08:23.908 --> 00:08:27.371 gas emissions and 2020 being the year that they peaked.