WEBVTT 00:00:00.000 --> 00:00:06.930 i'm going to give you a an overview of 00:00:02.820 --> 00:00:10.620 what it is that that we do as a as a 00:00:06.930 --> 00:00:13.830 group and what we do collectively as 00:00:10.620 --> 00:00:16.830 scientists to try and understand what 00:00:13.830 --> 00:00:19.109 we're dealing with with with climate and 00:00:16.830 --> 00:00:25.560 the climate system and climate change 00:00:19.109 --> 00:00:28.529 the world is extremely complex and 00:00:25.560 --> 00:00:32.339 dynamic the patterns that you can see 00:00:28.529 --> 00:00:34.140 here in these clouds which is not real 00:00:32.340 --> 00:00:37.350 where this is a computer simulations is 00:00:34.140 --> 00:00:41.520 not this is this isn't a this is in a on 00:00:37.350 --> 00:00:43.260 a laptop not on a non a satellite but 00:00:41.520 --> 00:00:44.640 the patterns that you can see a very 00:00:43.260 --> 00:00:48.599 similar to the ones that you see in the 00:00:44.640 --> 00:00:52.469 satellite you can see storms you can see 00:00:48.600 --> 00:00:54.449 convection you can see waves going 00:00:52.469 --> 00:00:56.430 through you can see things repeating but 00:00:54.449 --> 00:00:58.320 not quite right 00:00:56.430 --> 00:00:59.609 that's the essence of the system that 00:00:58.320 --> 00:01:02.340 were talking about it's a it's a 00:00:59.609 --> 00:01:05.400 complicated chaotic dynamic system it 00:01:02.340 --> 00:01:06.540 never quite repeats and yet all of the 00:01:05.400 --> 00:01:08.490 processes that are going on the 00:01:06.540 --> 00:01:10.890 underlying all of the things that are 00:01:08.490 --> 00:01:13.770 going on with these clouds there 00:01:10.890 --> 00:01:15.119 understandable there are computable we 00:01:13.770 --> 00:01:17.610 can go and measure all of those 00:01:15.119 --> 00:01:23.100 different individual things how do we 00:01:17.610 --> 00:01:26.340 deal with that the challenge is is one 00:01:23.100 --> 00:01:29.850 of scale the scales of the climate 00:01:26.340 --> 00:01:32.579 system range from micrometers for small 00:01:29.850 --> 00:01:36.449 aerosol particles that are from the 00:01:32.579 --> 00:01:38.639 nuclei of clouds in the atmosphere all 00:01:36.450 --> 00:01:40.950 the way out to the size of the planet 00:01:38.640 --> 00:01:42.780 itself which is about 10 to the 8th 00:01:40.950 --> 00:01:45.869 meters that's about 14 orders of 00:01:42.780 --> 00:01:48.329 magnitude that's an enormous scale range 00:01:45.869 --> 00:01:52.530 in which to encapsulate all the things 00:01:48.329 --> 00:01:54.210 that are going on and even in time you 00:01:52.530 --> 00:01:56.490 know you're going from things that are 00:01:54.210 --> 00:01:57.779 happening on micro second scales to 00:01:56.490 --> 00:02:01.140 things that are happening over millennia 00:01:57.780 --> 00:02:04.170 again 14 orders of magnitude an enormous 00:02:01.140 --> 00:02:06.900 range of scales to comprehend them play 00:02:04.170 --> 00:02:09.690 everything together that's enormous 00:02:06.900 --> 00:02:12.360 challenge what you have when you build a 00:02:09.690 --> 00:02:13.800 model then is-is-is you have some 00:02:12.360 --> 00:02:17.940 fundamental concerns we don't have 00:02:13.800 --> 00:02:21.150 infinite computer power right so how 00:02:17.940 --> 00:02:23.100 does that work well with weather models 00:02:21.150 --> 00:02:24.720 right the ones that produce the forecast 00:02:23.100 --> 00:02:26.820 that you see every day 00:02:24.720 --> 00:02:28.290 the kind that the kind of result physics 00:02:26.820 --> 00:02:30.720 the things that we can expressly 00:02:28.290 --> 00:02:33.900 included in these models go from the 00:02:30.720 --> 00:02:35.400 global scale down to about the 00:02:33.900 --> 00:02:38.820 50-kilometer scale right that's only a 00:02:35.400 --> 00:02:41.190 very small part of that huge range of 00:02:38.820 --> 00:02:43.530 scales that that actually impact of 00:02:41.190 --> 00:02:45.000 climate and the weather right the stuff 00:02:43.530 --> 00:02:46.860 that we can resolve the stuff that we 00:02:45.000 --> 00:02:49.140 can say okay we totally understand that 00:02:46.860 --> 00:02:51.570 we can put in the exact equations is 00:02:49.140 --> 00:02:54.420 just that small part all the rest of it 00:02:51.570 --> 00:02:57.810 is what we call these subscale processes 00:02:54.420 --> 00:03:00.149 now that stuff is is how a cloud 00:02:57.810 --> 00:03:02.250 actually forms how rainfall actually 00:03:00.150 --> 00:03:05.400 comes from a cloud system how 00:03:02.250 --> 00:03:07.950 evaporation works at other very very 00:03:05.400 --> 00:03:10.320 small scale and all of those things need 00:03:07.950 --> 00:03:14.220 to be approximated in some way we need 00:03:10.320 --> 00:03:17.880 to have some empirical phenomenological 00:03:14.220 --> 00:03:20.580 approximation to that physics to allow 00:03:17.880 --> 00:03:23.400 the rest of it to work and that's a real 00:03:20.580 --> 00:03:25.290 challenge right there's this is this is 00:03:23.400 --> 00:03:27.959 turbulence this is a small-scale 00:03:25.290 --> 00:03:30.329 heterogeneity this is small mountains 00:03:27.959 --> 00:03:32.100 and small hills and small lakes all of 00:03:30.330 --> 00:03:34.380 those things have to be squeezed into 00:03:32.100 --> 00:03:37.440 our approximation of those subscale 00:03:34.380 --> 00:03:40.200 processes so there's no guarantee that 00:03:37.440 --> 00:03:42.750 this works right there's no guarantee 00:03:40.200 --> 00:03:47.880 that this is even a program that will 00:03:42.750 --> 00:03:50.459 lead to successful predictions and so 00:03:47.880 --> 00:03:52.829 the test all of this program is whether 00:03:50.459 --> 00:03:53.790 it does actually produce successful 00:03:52.830 --> 00:03:56.310 predictions 00:03:53.790 --> 00:03:58.290 now you might not like the weather 00:03:56.310 --> 00:03:59.580 forecast that you get you might think 00:03:58.290 --> 00:04:01.380 that they're terrible but actually 00:03:59.580 --> 00:04:03.930 they're much much better than they used 00:04:01.380 --> 00:04:07.140 to be where the models are skillful of 00:04:03.930 --> 00:04:10.410 producing forecasts three four five six 00:04:07.140 --> 00:04:13.500 days almost 10 days out in ways that 00:04:10.410 --> 00:04:16.168 were unforeseen able even 20 years ago 00:04:13.500 --> 00:04:19.858 now climate models are slightly 00:04:16.168 --> 00:04:22.919 different beast climate models have to 00:04:19.858 --> 00:04:24.990 use longer timescales because time is a 00:04:22.919 --> 00:04:26.729 longer time scale and so that compromise 00:04:24.990 --> 00:04:27.520 they make is they don't go to quite such 00:04:26.729 --> 00:04:29.200 fine detail 00:04:27.520 --> 00:04:31.750 and so back in the nineteen nineties 00:04:29.200 --> 00:04:33.849 climate models really only occupied that 00:04:31.750 --> 00:04:38.199 very small part of that of that space 00:04:33.849 --> 00:04:40.659 now we can go a little bit further so in 00:04:38.199 --> 00:04:42.400 the 20,000 tens that so the models that 00:04:40.659 --> 00:04:45.190 were working with now you know we're 00:04:42.400 --> 00:04:47.770 coming out about the same spatial 00:04:45.190 --> 00:04:49.870 resolution as the weather models and 00:04:47.770 --> 00:04:52.210 we're taking up more times you know 00:04:49.870 --> 00:04:53.620 we're going out for a thousand years and 00:04:52.210 --> 00:04:56.289 working on the physics at the same 00:04:53.620 --> 00:04:58.659 potential and yet we still have this 00:04:56.289 --> 00:05:00.550 large large range of subjects scale 00:04:58.659 --> 00:05:07.840 processes that we still have to include 00:05:00.550 --> 00:05:09.370 this is a climate model I this is an old 00:05:07.840 --> 00:05:11.948 tram or you'll be pleased to know we 00:05:09.370 --> 00:05:14.409 don't use punch cards anymore it's a 00:05:11.949 --> 00:05:16.120 single line of Fortran we still do you 00:05:14.409 --> 00:05:18.280 use for transfer any of the old-timers 00:05:16.120 --> 00:05:19.870 here who think that that their skills 00:05:18.280 --> 00:05:21.758 are no longer valid 00:05:19.870 --> 00:05:25.240 they asked a valid yes you can have a 00:05:21.759 --> 00:05:26.740 job with each of these colored bands 00:05:25.240 --> 00:05:28.719 with a single subroutine a single 00:05:26.740 --> 00:05:30.699 calculation of some physical aspect of 00:05:28.719 --> 00:05:32.770 the code arm and you would put them into 00:05:30.699 --> 00:05:33.880 a machine one at a time and if you got 00:05:32.770 --> 00:05:36.250 them in the wrong order you have to 00:05:33.880 --> 00:05:39.849 start over again it would take months to 00:05:36.250 --> 00:05:42.390 produce any output arm and it was a very 00:05:39.849 --> 00:05:44.289 very clunky thing and so obviously if 00:05:42.390 --> 00:05:46.150 you have to write out every line using 00:05:44.289 --> 00:05:48.550 punch cards you don't include or of 00:05:46.150 --> 00:05:49.508 comments so you know we inherited this 00:05:48.550 --> 00:05:50.919 code and we're going 00:05:49.509 --> 00:05:52.990 what does this go do we have no idea 00:05:50.919 --> 00:05:57.940 anyway so it doesn't quite look like 00:05:52.990 --> 00:06:00.520 that anymore but the the essence the the 00:05:57.940 --> 00:06:02.740 idea of what we're doing is directly 00:06:00.520 --> 00:06:04.990 related to what we did back in the 00:06:02.740 --> 00:06:08.680 nineteen eighties and in the missus 00:06:04.990 --> 00:06:10.750 before that 1970 ok so how do we 00:06:08.680 --> 00:06:13.150 actually go around building a model we 00:06:10.750 --> 00:06:16.539 do it one piece of the time and i use 00:06:13.150 --> 00:06:17.770 the a jigsaw analogy by the beginning 00:06:16.539 --> 00:06:20.830 and I'll kind of work with that a little 00:06:17.770 --> 00:06:26.198 bit now it's very much like putting 00:06:20.830 --> 00:06:28.539 together pieces of a jigsaw so this is a 00:06:26.199 --> 00:06:31.719 piece of the jigsaw it's a picture of 00:06:28.539 --> 00:06:34.389 arctic sea ice taken from a flight going 00:06:31.719 --> 00:06:36.820 across the North Pole each of those ice 00:06:34.389 --> 00:06:38.919 floes that you can barely see there are 00:06:36.820 --> 00:06:39.860 a few tens of kilometers across and you 00:06:38.919 --> 00:06:42.169 can see leads 00:06:39.860 --> 00:06:43.520 the middle i was the summertime so the 00:06:42.169 --> 00:06:46.188 ice is breaking up 00:06:43.520 --> 00:06:47.659 and so there's a lot of physics is going 00:06:46.189 --> 00:06:50.300 on there right there is the physics of 00:06:47.659 --> 00:06:51.530 the Sun coming in reflecting off the ice 00:06:50.300 --> 00:06:53.810 because it's white 00:06:51.530 --> 00:06:56.599 there's the physics of the of the the 00:06:53.810 --> 00:06:58.159 heat being absorbed in the ice melting 00:06:56.599 --> 00:07:00.200 it from the top and is melting from the 00:06:58.159 --> 00:07:02.240 bottom going on at the same time there's 00:07:00.200 --> 00:07:04.370 dynamics how each of the ice floes 00:07:02.240 --> 00:07:07.390 interacts with each other all of those 00:07:04.370 --> 00:07:10.390 things can be encapsulated measured and 00:07:07.390 --> 00:07:11.389 put into some kind of formula so here 00:07:10.390 --> 00:07:18.529 are some of the formulas 00:07:11.389 --> 00:07:20.569 yeah so physics you know I don't expect 00:07:18.529 --> 00:07:22.580 you two to look at these your critique 00:07:20.569 --> 00:07:23.750 these are but this is basically what we 00:07:22.580 --> 00:07:25.609 do we write down what the boundary 00:07:23.750 --> 00:07:28.520 conditions are we use calculus we use 00:07:25.610 --> 00:07:31.390 basic conservation of energy that's 00:07:28.520 --> 00:07:34.849 that's a big deal and for each of those 00:07:31.390 --> 00:07:37.680 different things we then take some code 00:07:34.849 --> 00:07:39.110 and you get lots and lots of lines of 00:07:37.690 --> 00:07:42.500 code there are some comments now that 00:07:39.110 --> 00:07:45.349 that's pleasing arm mr. the last bit 00:07:42.500 --> 00:07:49.400 that there's some melting and we make 00:07:45.349 --> 00:07:51.650 that one piece into like a component and 00:07:49.400 --> 00:07:52.940 so okay well when we do see ice that's 00:07:51.650 --> 00:07:56.628 the piece of code that we're going to 00:07:52.940 --> 00:07:58.789 use and we can add in lots of different 00:07:56.629 --> 00:08:01.159 processes so that was the sea-ice 00:07:58.789 --> 00:08:04.219 process now there's one other processes 00:08:01.159 --> 00:08:08.930 associated with clouds there's a process 00:08:04.219 --> 00:08:10.460 associated with radiation and the solar 00:08:08.930 --> 00:08:12.319 radiation coming through the atmosphere 00:08:10.460 --> 00:08:14.568 and being absorbed at the different 00:08:12.319 --> 00:08:19.639 layers of the atmosphere that's one more 00:08:14.569 --> 00:08:23.120 piece there are other pieces the winds 00:08:19.639 --> 00:08:25.699 and the way use and other pieces the 00:08:23.120 --> 00:08:27.560 flow of water through plants the flow of 00:08:25.699 --> 00:08:31.189 water and rivers back down to the ocean 00:08:27.560 --> 00:08:35.240 so the point is that each of those bits 00:08:31.189 --> 00:08:37.849 makes up part of the picture of the 00:08:35.240 --> 00:08:40.700 climate system now I've left and pieces 00:08:37.849 --> 00:08:42.799 out because our picture of the timing 00:08:40.700 --> 00:08:46.430 system is not complete right we don't 00:08:42.799 --> 00:08:51.109 know everything about the system and yet 00:08:46.430 --> 00:08:53.479 when we put it all together we end up 00:08:51.110 --> 00:08:56.870 with a simulation 00:08:53.480 --> 00:09:00.139 that has all of the emergent properties 00:08:56.870 --> 00:09:03.790 that we can see in the real world right 00:09:00.139 --> 00:09:05.720 so these storm systems in the Southern 00:09:03.790 --> 00:09:07.279 Ocean you can anybody has been to the 00:09:05.720 --> 00:09:09.440 Southern Ocean knows exactly what they 00:09:07.279 --> 00:09:11.600 look like or storms in the North 00:09:09.440 --> 00:09:16.100 Atlantic Kevin can tell you about those 00:09:11.600 --> 00:09:19.790 tropical cyclones in in the Pacific the 00:09:16.100 --> 00:09:21.380 convective bands in in the was a couple 00:09:19.790 --> 00:09:23.839 of tropical cyclones are going to cycle 00:09:21.380 --> 00:09:29.600 around each other kind of meat 00:09:23.839 --> 00:09:32.329 yeah now within the code there was no 00:09:29.600 --> 00:09:35.149 code that says hey do an atmospheric 00:09:32.329 --> 00:09:37.910 River that hits Oregon there's no code 00:09:35.149 --> 00:09:40.160 that says do tropical cyclones and make 00:09:37.910 --> 00:09:42.260 them dance around each other right 00:09:40.160 --> 00:09:45.230 all of these things are emergent 00:09:42.260 --> 00:09:47.360 properties that just arise from the fact 00:09:45.230 --> 00:09:50.290 that the system that you're modeling is 00:09:47.360 --> 00:09:51.589 chaotic is dynamic and all of the 00:09:50.290 --> 00:09:54.949 different processes that we put together 00:09:51.589 --> 00:10:04.579 intersect and interact in ways that you 00:09:54.949 --> 00:10:09.439 can't predict a priori now just having 00:10:04.579 --> 00:10:12.800 done that i think is a intellectual 00:10:09.440 --> 00:10:14.810 endeavor worthy of of of Cato 00:10:12.800 --> 00:10:16.939 and-and-and Chomsky right trying to 00:10:14.810 --> 00:10:18.589 understand exactly what's going on in 00:10:16.940 --> 00:10:21.620 such a complex system and being 00:10:18.589 --> 00:10:24.500 successful at doing so is an enormous 00:10:21.620 --> 00:10:28.399 challenge and i think one we can rightly 00:10:24.500 --> 00:10:31.519 be proud of but we're not just doing it 00:10:28.399 --> 00:10:35.149 to understand the system we're doing it 00:10:31.519 --> 00:10:37.610 because that system can be kicked in 00:10:35.149 --> 00:10:40.310 many many different ways and right now 00:10:37.610 --> 00:10:43.190 humans are kicking this system in a very 00:10:40.310 --> 00:10:44.930 particular way so let's look at some 00:10:43.190 --> 00:10:47.000 ways in which the system can be kept 00:10:44.930 --> 00:10:49.880 right so there are waffles in the 00:10:47.000 --> 00:10:51.860 Earth's orbit these bubbles kind of make 00:10:49.880 --> 00:10:54.529 a difference on ten thousand two hundred 00:10:51.860 --> 00:10:57.740 thousand year time scales and a big 00:10:54.529 --> 00:10:59.660 driver of the of the of the Ice Age 00:10:57.740 --> 00:11:04.690 cycle that we've been seeing for the 00:10:59.660 --> 00:11:05.569 past 2.5 million years right so Iceland 00:11:04.690 --> 00:11:06.979 used to have a lot more ice 00:11:05.569 --> 00:11:10.130 it's not quite as I see 00:11:06.980 --> 00:11:14.209 as it used to be and and and it will get 00:11:10.130 --> 00:11:15.470 messy as well with 10,000 years ago 00:11:14.209 --> 00:11:16.849 20,000 years ago 00:11:15.470 --> 00:11:20.360 Iceland was almost completely emaciated 00:11:16.850 --> 00:11:21.860 right all right yeah and that's due to 00:11:20.360 --> 00:11:24.589 these bubbles so that's that's a very 00:11:21.860 --> 00:11:26.300 powerful kick to the system right that's 00:11:24.589 --> 00:11:29.660 everything changed 00:11:26.300 --> 00:11:32.389 you know can we understand that ok there 00:11:29.660 --> 00:11:35.290 are changes because of the Sun the Sun 00:11:32.389 --> 00:11:37.190 has cycles that has activity and it's 00:11:35.290 --> 00:11:40.459 over its lifetime of the lifetime of the 00:11:37.190 --> 00:11:42.470 earth has expanded and become more 00:11:40.459 --> 00:11:44.599 active by about thirty percent over the 00:11:42.470 --> 00:11:46.880 last four billion years that has an 00:11:44.600 --> 00:11:50.890 impact on the climate the set the solar 00:11:46.880 --> 00:11:52.220 cycles an 11-year cycle have an impact 00:11:50.890 --> 00:11:58.400 on the climate we need to understand 00:11:52.220 --> 00:12:00.800 those things volcanoes as have also well 00:11:58.400 --> 00:12:02.689 aware have an impact on the climate not 00:12:00.800 --> 00:12:06.229 just locally but they can have a global 00:12:02.690 --> 00:12:07.820 impact on the climate by the injection 00:12:06.230 --> 00:12:10.130 of sulfates into the stratosphere 00:12:07.820 --> 00:12:11.420 changing the albedo of the palette 00:12:10.130 --> 00:12:14.180 changing the amount of energy coming 00:12:11.420 --> 00:12:16.399 into the system right so you're getting 00:12:14.180 --> 00:12:20.779 the idea there are lots of different 00:12:16.399 --> 00:12:23.600 ways in which we can change the climate 00:12:20.779 --> 00:12:25.430 right or the system itself can be 00:12:23.600 --> 00:12:28.100 changed whether its biomass burning 00:12:25.430 --> 00:12:31.579 ozone depletion land-use change 00:12:28.100 --> 00:12:35.449 contrails or of course greenhouse gases 00:12:31.579 --> 00:12:37.579 all of these change the balances and the 00:12:35.449 --> 00:12:39.380 flows of energy in the system and when 00:12:37.579 --> 00:12:40.969 you change the balances and flows of 00:12:39.380 --> 00:12:49.100 energy in the system you change the 00:12:40.970 --> 00:12:51.190 climate so what we need to understand is 00:12:49.100 --> 00:12:53.600 whether the simulations that i discussed 00:12:51.190 --> 00:12:56.180 before where the weather models are the 00:12:53.600 --> 00:12:57.768 climate models whether they have skill I 00:12:56.180 --> 00:12:59.719 want to be very clear about this 00:12:57.769 --> 00:13:02.510 these models are not complete right 00:12:59.720 --> 00:13:04.250 there were holes in the jigsaw there's 00:13:02.510 --> 00:13:07.610 whole bunches of things that we have to 00:13:04.250 --> 00:13:10.519 and empirically fill-in write the word 00:13:07.610 --> 00:13:12.680 that we can't predict from a priori 00:13:10.519 --> 00:13:16.339 considerations 00:13:12.680 --> 00:13:17.300 so why do we think that these things are 00:13:16.339 --> 00:13:19.310 useful 00:13:17.300 --> 00:13:20.258 we think that they're useful because 00:13:19.310 --> 00:13:24.608 they have 00:13:20.259 --> 00:13:26.979 demonstrated skill skill is I model 00:13:24.609 --> 00:13:28.689 results skillful if it's better than 00:13:26.979 --> 00:13:31.569 what you would have had otherwise 00:13:28.689 --> 00:13:34.540 that's not to say it's perfect it's not 00:13:31.569 --> 00:13:36.219 to say that there are uncertainties but 00:13:34.540 --> 00:13:38.858 it's something that's better than what 00:13:36.220 --> 00:13:41.889 you had before with the weather forecast 00:13:38.859 --> 00:13:43.720 you could stick your finger in the air 00:13:41.889 --> 00:13:46.539 and predict what the weather is going to 00:13:43.720 --> 00:13:48.549 be tomorrow based on just persistence of 00:13:46.539 --> 00:13:50.559 the weather today that probably doesn't 00:13:48.549 --> 00:13:54.390 work very well here but it works quite 00:13:50.559 --> 00:13:56.319 well in New York but we can do better 00:13:54.390 --> 00:13:58.779 than that with models right weather 00:13:56.319 --> 00:14:00.189 models a skillful despite the fact that 00:13:58.779 --> 00:14:03.189 there was that whole range of things 00:14:00.189 --> 00:14:05.919 that we had to empirically include and 00:14:03.189 --> 00:14:09.399 so we need to demonstrate that climate 00:14:05.919 --> 00:14:11.649 models are skillful at estimating the 00:14:09.399 --> 00:14:13.720 changes to the climate when you kick 00:14:11.649 --> 00:14:15.789 that system in all of the different 00:14:13.720 --> 00:14:16.600 myriad ways that that system can be 00:14:15.789 --> 00:14:19.239 kicked 00:14:16.600 --> 00:14:22.290 okay so is that true is there are the 00:14:19.239 --> 00:14:24.999 models skillful so well they know 00:14:22.290 --> 00:14:27.759 volcanoes are a current topic of 00:14:24.999 --> 00:14:29.289 interest in in Iceland I said well 00:14:27.759 --> 00:14:31.660 actually not not anymore right we're 00:14:29.289 --> 00:14:33.850 done with the volcanoes right so that's 00:14:31.660 --> 00:14:36.999 it for the next week right 00:14:33.850 --> 00:14:40.590 remember no more volcanoes ok 00:14:36.999 --> 00:14:42.519 all models skillful with respect to big 00:14:40.590 --> 00:14:45.129 volcanic forces so the large big volcano 00:14:42.519 --> 00:14:47.190 that we had that had a global impact was 00:14:45.129 --> 00:14:51.369 magnitude but went off in june nineteen 00:14:47.190 --> 00:14:54.399 ninety one arm and this is a graph of 00:14:51.369 --> 00:14:56.889 how much stuff basically there was in 00:14:54.399 --> 00:14:59.169 the stratosphere are from the main 00:14:56.889 --> 00:15:01.359 eruption and then it took like three or 00:14:59.169 --> 00:15:02.980 four years for all that stuff to kind of 00:15:01.359 --> 00:15:05.289 fall out of the atmosphere 00:15:02.980 --> 00:15:07.749 ok so this is actually quite a large 00:15:05.289 --> 00:15:09.669 amount of stuff right on the amount of 00:15:07.749 --> 00:15:13.329 stuff that that is there that's the 00:15:09.669 --> 00:15:17.100 technical term stuff and got some people 00:15:13.329 --> 00:15:21.209 pay attention okay 00:15:17.100 --> 00:15:24.450 the amount of stuff that was there cause 00:15:21.210 --> 00:15:26.640 the radiation to be from the Sun to be 00:15:24.450 --> 00:15:28.530 significantly less than it was right 00:15:26.640 --> 00:15:31.710 because each of those little particles 00:15:28.530 --> 00:15:33.360 is white and so when the Sun shines on a 00:15:31.710 --> 00:15:35.910 white particle it reflects back to space 00:15:33.360 --> 00:15:37.560 and that reduces the total amount of 00:15:35.910 --> 00:15:39.569 energy coming in the amount of energy 00:15:37.560 --> 00:15:41.459 going out was pretty much the same and 00:15:39.570 --> 00:15:43.650 so you have less energy coming into the 00:15:41.460 --> 00:15:46.620 system right so basic conservation of 00:15:43.650 --> 00:15:48.660 energy suggest that that would lead to a 00:15:46.620 --> 00:15:51.930 cooling of the planet but by how much 00:15:48.660 --> 00:15:53.819 how much should the planet call with a 3 00:15:51.930 --> 00:15:57.239 watt per meter squared energy imbalance 00:15:53.820 --> 00:15:59.160 over a few years you have to do the 00:15:57.240 --> 00:16:02.100 calculation and the climate models allow 00:15:59.160 --> 00:16:04.410 you to do that calculation so what do 00:16:02.100 --> 00:16:06.990 they suggest well what they suggested 00:16:04.410 --> 00:16:09.300 are the the little thin lines that you 00:16:06.990 --> 00:16:10.350 can see there's a bit of noise because 00:16:09.300 --> 00:16:13.140 of the different weather and each of 00:16:10.350 --> 00:16:14.670 those models and then the red line there 00:16:13.140 --> 00:16:17.850 is what actually happened 00:16:14.670 --> 00:16:21.270 so the models were able to estimate 00:16:17.850 --> 00:16:23.160 quite precisely the rate at which this 00:16:21.270 --> 00:16:26.760 the climate called because of this 00:16:23.160 --> 00:16:28.949 forcing and we know that is better than 00:16:26.760 --> 00:16:30.180 what we could just worked out by doing a 00:16:28.950 --> 00:16:32.430 calculation on the back of the envelope 00:16:30.180 --> 00:16:35.280 and in fact the first time that we did 00:16:32.430 --> 00:16:39.510 that calculation we did it in October 00:16:35.280 --> 00:16:41.970 1991 and made this prediction before any 00:16:39.510 --> 00:16:45.300 of those changes had actually occurred 00:16:41.970 --> 00:16:47.370 the model was skillful and it wasn't 00:16:45.300 --> 00:16:49.589 just fearful estimating the global 00:16:47.370 --> 00:16:51.330 cooling which you know kind of my energy 00:16:49.590 --> 00:16:54.540 balance arguments you might argue was 00:16:51.330 --> 00:16:58.350 the easy part but it was also skillful 00:16:54.540 --> 00:17:01.500 at predicting that in the wintertime you 00:16:58.350 --> 00:17:03.570 got a strange pattern in Europe where 00:17:01.500 --> 00:17:06.210 you actually get winter warming after a 00:17:03.570 --> 00:17:08.970 big volcano and that turns out to be a 00:17:06.210 --> 00:17:10.770 dynamic response changes in the winds 00:17:08.970 --> 00:17:13.800 that are affected by the temperature 00:17:10.770 --> 00:17:17.670 changes our loft that actually push more 00:17:13.800 --> 00:17:19.680 warm water over more warm air over over 00:17:17.670 --> 00:17:21.450 Europe during the wintertime and that is 00:17:19.680 --> 00:17:24.000 also captured by the model and the 00:17:21.450 --> 00:17:26.099 models are skillful even with the 00:17:24.000 --> 00:17:29.280 dynamics and the radiation and the 00:17:26.099 --> 00:17:30.169 temperature there are lots of other 00:17:29.280 --> 00:17:32.299 example 00:17:30.169 --> 00:17:34.159 solar cycles you know we can measure and 00:17:32.299 --> 00:17:36.200 calculate the change in ozone in the 00:17:34.159 --> 00:17:38.419 stratosphere because of this change in 00:17:36.200 --> 00:17:41.840 the sun with models are skillful because 00:17:38.419 --> 00:17:44.179 of that in overall changes those wobbles 00:17:41.840 --> 00:17:46.369 in the Earth's orbit like even 6,000 00:17:44.179 --> 00:17:48.139 years ago they were relatively important 00:17:46.369 --> 00:17:50.629 and we can look at that difference and 00:17:48.139 --> 00:17:52.908 the models are skillful estimating how 00:17:50.629 --> 00:17:55.129 the northern hemisphere temperatures got 00:17:52.909 --> 00:17:58.399 better because our change because of 00:17:55.129 --> 00:18:01.700 that ok 00:17:58.399 --> 00:18:03.139 the response to the ice sheets 20,000 00:18:01.700 --> 00:18:04.129 years ago the models are successful are 00:18:03.139 --> 00:18:06.289 getting that right 00:18:04.129 --> 00:18:07.908 the 20th century multi-decade all trends 00:18:06.289 --> 00:18:10.940 were successful getting that right 00:18:07.909 --> 00:18:12.109 models are skillful even bizarre things 00:18:10.940 --> 00:18:14.629 that have happened to the climate about 00:18:12.109 --> 00:18:17.590 8,000 years ago there was a huge great 00:18:14.629 --> 00:18:18.590 lake that covered most of Manitoba and 00:18:17.590 --> 00:18:20.749 Ontario much larger than all of the 00:18:18.590 --> 00:18:25.369 great lakes that exists right now and it 00:18:20.749 --> 00:18:27.980 was kept in place by the remnant by the 00:18:25.369 --> 00:18:30.350 remnant ice sheet that was kind of 00:18:27.980 --> 00:18:32.929 standing over hudson bay about 8,000 00:18:30.350 --> 00:18:34.519 years ago that I sheet finally broke and 00:18:32.929 --> 00:18:37.900 all of that water that was kept in that 00:18:34.519 --> 00:18:38.629 Lake rushed into hudson bay and into the 00:18:37.900 --> 00:18:41.659 labrador sea and into the North Atlantic 00:18:38.629 --> 00:18:43.730 around here and at that same time there 00:18:41.659 --> 00:18:46.190 is evidence of a cooling event that 00:18:43.730 --> 00:18:48.350 happened in the Greenland ice cause in 00:18:46.190 --> 00:18:49.850 Europe and in Newfoundland and all 00:18:48.350 --> 00:18:52.189 around here and I'm sure that they would 00:18:49.850 --> 00:18:55.340 a nice and have been affected as well 00:18:52.190 --> 00:18:57.799 the models are skillful at responding to 00:18:55.340 --> 00:19:00.619 that water going in by changing the 00:18:57.799 --> 00:19:01.908 circulation in the in the ocean and by 00:19:00.619 --> 00:19:03.379 changing the temperatures in the 00:19:01.909 --> 00:19:05.600 rainfall patterns associated with that 00:19:03.379 --> 00:19:08.209 the models are skillful across a whole 00:19:05.600 --> 00:19:09.320 range of different ways that we can kick 00:19:08.210 --> 00:19:14.130 that system 00:19:09.320 --> 00:19:17.610 ok 00:19:14.130 --> 00:19:20.910 and that system is complicated and 00:19:17.610 --> 00:19:23.969 global right this is a simulation again 00:19:20.910 --> 00:19:25.110 of tiny little atmospheric particles and 00:19:23.970 --> 00:19:28.590 all the different kinds of particles 00:19:25.110 --> 00:19:31.500 that you can have these orange swirls 00:19:28.590 --> 00:19:33.300 are dust coming from the Sahara Desert 00:19:31.500 --> 00:19:35.909 and you can see them affecting the 00:19:33.300 --> 00:19:37.770 climate and affecting a deposition of 00:19:35.910 --> 00:19:41.430 stuff all the way across the Atlantic 00:19:37.770 --> 00:19:43.320 the white wispy parts over over Europe 00:19:41.430 --> 00:19:45.270 you can see that's atmospheric pollution 00:19:43.320 --> 00:19:47.220 sulfates right and you can see that 00:19:45.270 --> 00:19:50.760 what's happens in Europe does not stay 00:19:47.220 --> 00:19:53.250 in Europe the green and the Reds 00:19:50.760 --> 00:19:54.780 indicate where there is our where there 00:19:53.250 --> 00:19:57.000 are fires and whether its biomass 00:19:54.780 --> 00:19:58.470 burning and where is organic carbon and 00:19:57.000 --> 00:20:01.170 black carbon being put into the 00:19:58.470 --> 00:20:02.940 atmosphere and again these things don't 00:20:01.170 --> 00:20:04.950 just stay where they are stuck there 00:20:02.940 --> 00:20:08.190 they started you can see the pollution 00:20:04.950 --> 00:20:12.480 over China that again does not just stay 00:20:08.190 --> 00:20:15.300 in China the blue dots associated with 00:20:12.480 --> 00:20:17.850 the big tropical storms are associated 00:20:15.300 --> 00:20:20.610 with sea salt particles so as the winds 00:20:17.850 --> 00:20:23.280 whip up the waves small particles of sea 00:20:20.610 --> 00:20:26.370 salt which are a key element in the 00:20:23.280 --> 00:20:28.440 production of low-level clouds you can 00:20:26.370 --> 00:20:32.159 see them again in the in the Southern 00:20:28.440 --> 00:20:35.610 Ocean all of these things are connected 00:20:32.160 --> 00:20:38.250 and important and we can answer now with 00:20:35.610 --> 00:20:40.500 the click with the with the computer 00:20:38.250 --> 00:20:42.300 models that we have we can answer 00:20:40.500 --> 00:20:43.860 questions that associate that are 00:20:42.300 --> 00:20:47.700 associated with all of those things 00:20:43.860 --> 00:20:52.979 how does pollution change climate and 00:20:47.700 --> 00:20:55.530 air quality all at the same time I love 00:20:52.980 --> 00:20:57.240 this but this this animation that they 00:20:55.530 --> 00:20:59.970 they did a really nice job here this is 00:20:57.240 --> 00:21:01.470 my colleagues at NASA Goddard Space 00:20:59.970 --> 00:21:03.510 Flight Center and now there's another 00:21:01.470 --> 00:21:06.450 volcano in Madagascar that just went off 00:21:03.510 --> 00:21:08.400 and so you can include all thoughts of 00:21:06.450 --> 00:21:10.560 things in these models and answer all 00:21:08.400 --> 00:21:15.460 sorts of actually quite subtle and 00:21:10.560 --> 00:21:19.990 interesting nuance questions 00:21:15.460 --> 00:21:22.570 how things work over the 20th century 00:21:19.990 --> 00:21:25.590 when we've seen an amount of global 00:21:22.570 --> 00:21:28.590 warming right so is this is a model 00:21:25.590 --> 00:21:30.789 simulation this is the observations you 00:21:28.590 --> 00:21:32.620 can see the patterns of whether you know 00:21:30.789 --> 00:21:35.649 they're not correlated the weather isn't 00:21:32.620 --> 00:21:38.490 predictable 50 years in advance but the 00:21:35.649 --> 00:21:40.239 emerging patterns have changed that you 00:21:38.490 --> 00:21:41.950 see towards the end of the 20th century 00:21:40.240 --> 00:21:45.399 and that we end up where we are today 00:21:41.950 --> 00:21:47.559 those patterns are predictable they are 00:21:45.399 --> 00:21:49.959 predicted by the models the models are 00:21:47.559 --> 00:21:51.970 skillful at getting these patterns right 00:21:49.960 --> 00:21:53.799 this warming in the Arctic compared to 00:21:51.970 --> 00:21:55.270 the Antarctic the warming over land 00:21:53.799 --> 00:21:57.549 compared to the ocean the warming in the 00:21:55.270 --> 00:22:04.210 North versus the woman in the south 00:21:57.549 --> 00:22:06.700 these are skillful models but then let's 00:22:04.210 --> 00:22:09.100 think about the real reason why we need 00:22:06.700 --> 00:22:12.668 models right and then this this comes 00:22:09.100 --> 00:22:14.620 from a rebuttal that the two scientists 00:22:12.669 --> 00:22:17.799 wrote when somebody you know they talked 00:22:14.620 --> 00:22:20.200 about modeling of of future tropical 00:22:17.799 --> 00:22:21.580 cyclones and somebody wrote a response 00:22:20.200 --> 00:22:24.100 to them they say well why are you 00:22:21.580 --> 00:22:28.149 looking observations and they responded 00:22:24.100 --> 00:22:30.340 i think quite finally what if we had 00:22:28.149 --> 00:22:32.590 observations of the future we obviously 00:22:30.340 --> 00:22:36.610 would trust them more than models but 00:22:32.590 --> 00:22:40.449 unfortunately observations of the future 00:22:36.610 --> 00:22:43.360 and not available at this time and 00:22:40.450 --> 00:22:45.429 that's funny but it's actually the real 00:22:43.360 --> 00:22:49.000 reason why we build models we want to 00:22:45.429 --> 00:22:51.130 have predictive capability of situations 00:22:49.000 --> 00:22:53.649 where we don't yet have any observations 00:22:51.130 --> 00:22:55.720 so that we can make plans accordingly 00:22:53.649 --> 00:22:57.610 whether it's a weather forecast whether 00:22:55.720 --> 00:22:59.830 it's a climate forecasts whether it's an 00:22:57.610 --> 00:23:03.908 economic projection which we could get 00:22:59.830 --> 00:23:06.939 into is as well but Sir what we want our 00:23:03.909 --> 00:23:10.270 is an ability to make informed decisions 00:23:06.940 --> 00:23:12.460 about the future right so predictable 00:23:10.270 --> 00:23:15.668 lity and predicting the future is the 00:23:12.460 --> 00:23:16.929 absolute fundamental reason why we're 00:23:15.669 --> 00:23:18.309 looking at models right that's what 00:23:16.929 --> 00:23:21.159 science is all about making predictions 00:23:18.309 --> 00:23:22.570 testing your theories adapting them 00:23:21.159 --> 00:23:26.799 making them better making them more 00:23:22.570 --> 00:23:27.679 predictive so what does the future hold 00:23:26.799 --> 00:23:31.430 what we have 00:23:27.680 --> 00:23:34.700 in the future of course our choices and 00:23:31.430 --> 00:23:37.580 we don't have to fall down one 00:23:34.700 --> 00:23:40.220 particular line the economic an economy 00:23:37.580 --> 00:23:42.350 technology how we structure societies 00:23:40.220 --> 00:23:44.810 these things are not written in stone 00:23:42.350 --> 00:23:50.510 we have choices society has choices you 00:23:44.810 --> 00:23:52.700 individuals have choices and these 00:23:50.510 --> 00:23:55.850 aren't you know completely accurate 00:23:52.700 --> 00:23:58.400 labels we don't know really what will 00:23:55.850 --> 00:24:02.000 happen if we just continue as we go 00:23:58.400 --> 00:24:03.830 along this is an estimate of that we 00:24:02.000 --> 00:24:06.170 have a pretty good idea of what it would 00:24:03.830 --> 00:24:09.230 take to bring everything kind of back 00:24:06.170 --> 00:24:12.650 down to the level that it was you know 00:24:09.230 --> 00:24:16.550 at the beginning of this century this 00:24:12.650 --> 00:24:18.350 aggressive mitigation i am kevin will 00:24:16.550 --> 00:24:21.860 tell you this is not going to happen 00:24:18.350 --> 00:24:25.340 this is the under two-degree world that 00:24:21.860 --> 00:24:26.270 people talk about sometimes business as 00:24:25.340 --> 00:24:29.720 usual 00:24:26.270 --> 00:24:31.160 that's a 56 degree world that's a 00:24:29.720 --> 00:24:33.140 totally different planet 00:24:31.160 --> 00:24:34.580 remember how different the ice age was 00:24:33.140 --> 00:24:36.950 to today 00:24:34.580 --> 00:24:39.439 well that is just as different but in 00:24:36.950 --> 00:24:42.140 the opposite direction the ice age was a 00:24:39.440 --> 00:24:44.510 different planet different organization 00:24:42.140 --> 00:24:47.510 of ecosystems where people lived where 00:24:44.510 --> 00:24:50.480 things live where things grew the same 00:24:47.510 --> 00:24:53.870 will be true for the business-as-usual 00:24:50.480 --> 00:24:58.490 planet where were more likely to end up 00:24:53.870 --> 00:25:00.649 in my opinion is some effort serious 00:24:58.490 --> 00:25:02.840 mitigation not today not tomorrow maybe 00:25:00.650 --> 00:25:05.450 in the next 10 years 20 years 30 is 00:25:02.840 --> 00:25:08.990 armed and now I'll still be a planet 00:25:05.450 --> 00:25:11.390 that has significantly warmer 00:25:08.990 --> 00:25:13.700 temperatures particularly on land 00:25:11.390 --> 00:25:16.760 particularly in the North particularly 00:25:13.700 --> 00:25:19.520 in the Arctic this will be a radically 00:25:16.760 --> 00:25:22.640 different planet as well but exactly how 00:25:19.520 --> 00:25:26.210 different is still to be determined but 00:25:22.640 --> 00:25:31.430 the choices are really ours to make 00:25:26.210 --> 00:25:33.740 now I'm a scientist and and I spend my 00:25:31.430 --> 00:25:35.750 time working on those small scale 00:25:33.740 --> 00:25:37.400 processes and the encapsulation of all 00:25:35.750 --> 00:25:39.299 of that physics that you store in those 00:25:37.400 --> 00:25:42.360 animations 00:25:39.299 --> 00:25:47.999 and these projections these predictions 00:25:42.360 --> 00:25:50.758 put us in a very odd position and it was 00:25:47.999 --> 00:25:56.639 very clearly encapsulated by showed 00:25:50.759 --> 00:25:59.820 Rowland who are was the one of the the 00:25:56.639 --> 00:26:01.738 chemists who discovered the reactions 00:25:59.820 --> 00:26:03.960 that led to ozone depletion and some of 00:26:01.739 --> 00:26:06.389 you here will remember spray cans and 00:26:03.960 --> 00:26:09.480 freon and the Montreal Protocol and how 00:26:06.389 --> 00:26:12.748 that was negotiated and how that changed 00:26:09.480 --> 00:26:15.600 so sure Roland understood quite clearly 00:26:12.749 --> 00:26:17.730 the consequences of having made 00:26:15.600 --> 00:26:22.259 scientific discoveries that have 00:26:17.730 --> 00:26:25.409 real-world implications and he said in 00:26:22.259 --> 00:26:27.389 an interview what's the use of having 00:26:25.409 --> 00:26:30.989 developed a science well enough to make 00:26:27.389 --> 00:26:33.269 predictions if in the end all willing to 00:26:30.989 --> 00:26:37.109 do is stand around and wait for them to 00:26:33.269 --> 00:26:41.279 come true and that's really the dilemma 00:26:37.109 --> 00:26:44.699 that people like me fais do we just 00:26:41.279 --> 00:26:46.649 continue to make predictions or do we go 00:26:44.700 --> 00:26:49.649 out and tell people about what these 00:26:46.649 --> 00:26:51.779 predictions mean do we go and help 00:26:49.649 --> 00:26:53.998 people work out what they should do 00:26:51.779 --> 00:26:57.119 about the energy system i'm not an 00:26:53.999 --> 00:26:58.679 expert in energy systems you know should 00:26:57.119 --> 00:27:00.590 we use nuclear power should be used 00:26:58.679 --> 00:27:01.109 geothermal power should we do this 00:27:00.590 --> 00:27:04.408 should we do that 00:27:01.109 --> 00:27:08.399 those are decisions that are not up to 00:27:04.409 --> 00:27:11.609 me though I would like to think that the 00:27:08.399 --> 00:27:14.639 information that we produce informs the 00:27:11.609 --> 00:27:16.918 decisions that you make individually and 00:27:14.639 --> 00:27:22.529 that you make as a city or as a country 00:27:16.919 --> 00:27:28.590 and as the world and I don't know what 00:27:22.529 --> 00:27:34.440 our future will hold arm but i'm i'm 00:27:28.590 --> 00:27:37.289 hopeful that whatever future we choose 00:27:34.440 --> 00:27:42.529 it's an informed future so thank you 00:27:37.289 --> 00:27:42.529 very much