2 00:00:10,397 --> 00:00:13,601 The future of fossil fuels can be projected 3 00:00:13,601 --> 00:00:17,339 with some amount of reason, by 4 00:00:17,339 --> 00:00:20,899 extrapolating from what is going on today 5 00:00:20,899 --> 00:00:24,800 and how we think things might change into the future. 6 00:00:24,800 --> 00:00:26,530 There are lots of different ways that you can 7 00:00:26,530 --> 00:00:28,890 do this scenario forecasting, some of them 8 00:00:28,890 --> 00:00:31,900 very complicated, that take into account the individual countries 9 00:00:31,900 --> 00:00:35,980 and individual situations, but you can also get there 10 00:00:35,980 --> 00:00:40,340 from a broader perspective using this 11 00:00:40,340 --> 00:00:42,770 formula, which is known as the Kaya identity. 12 00:00:44,220 --> 00:00:50,290 The rate of carbon emission can be calculated as the product of 13 00:00:50,290 --> 00:00:58,230 the population as you expect it to grow in the future, times the GDP per capita, 14 00:00:58,230 --> 00:01:00,980 because fossil fuel use is so 15 00:01:00,980 --> 00:01:03,180 closely tied with economic activity. 16 00:01:03,180 --> 00:01:07,610 If we look at the units that we're building up here, population is people. 17 00:01:07,610 --> 00:01:11,440 GDP per capita is dollars per person, per year. 18 00:01:11,440 --> 00:01:15,850 And so the units of people cancels out there. 19 00:01:17,180 --> 00:01:20,340 The third term is the energy intensity. 20 00:01:20,340 --> 00:01:23,210 This is basically how much energy 21 00:01:23,210 --> 00:01:25,998 it takes to make a dollar, to do a dollar's 22 00:01:25,998 --> 00:01:28,055 worth of economic activity. 23 00:01:28,055 --> 00:01:31,500 And this depends on whether you're making a dollar's worth of 24 00:01:31,500 --> 00:01:34,779 steel or a dollars worth of coffee or something like that. 25 00:01:34,779 --> 00:01:35,822 It makes a difference. 26 00:01:35,822 --> 00:01:40,428 It also depends on on energy efficiency. 27 00:01:40,428 --> 00:01:46,148 Now we've got watts per year. 28 00:01:46,148 --> 00:01:51,542 and last term is has to do with this energy source, 29 00:01:51,542 --> 00:01:57,688 how you're making the energy, the amount of carbon per watt of energy. 30 00:01:57,688 --> 00:02:03,612 Nuclear power would have less carbon per watt than coal production. 31 00:02:03,612 --> 00:02:06,420 The units now cancel, so we have watts or, 32 00:02:06,420 --> 00:02:10,450 gigatons of carbon per year. 33 00:02:11,780 --> 00:02:16,790 Extrapolating the present day trends 34 00:02:16,790 --> 00:02:21,340 in these terms, we need to guess how high 35 00:02:21,340 --> 00:02:25,200 we think earth's population is going to reach. 36 00:02:25,200 --> 00:02:28,680 Hopefully it will plateau and stop growing, it looks like it's doing that. 37 00:02:30,230 --> 00:02:36,750 The average income on the earth is increasing a function of time. 38 00:02:36,750 --> 00:02:41,168 We can put the rate of change of that into the equation. 39 00:02:41,168 --> 00:02:46,190 The energy use is getting more efficient. 40 00:02:46,190 --> 00:02:49,530 The energy intensity is decreasing through time. 41 00:02:49,530 --> 00:02:54,935 And then there are also changes in the carbon source that have to do with 42 00:02:54,935 --> 00:03:00,670 efficiency, but also there's been a recent trend away 43 00:03:00,670 --> 00:03:06,574 from coal because of lower prices for natural gases brought about 44 00:03:06,574 --> 00:03:11,610 by improvements in the ability to extract natural gas known as fracking. 45 00:03:13,090 --> 00:03:17,146 But you put all these things together, and you end up with 46 00:03:17,146 --> 00:03:22,294 the projection that under business as usual, that means with no effort to 47 00:03:22,294 --> 00:03:27,598 avoid climate change, the rate of carbon emission, today about 10 gigatons a 48 00:03:27,598 --> 00:03:32,247 year, could grow to about 20 gigatons a year by the year 2100.