Michael LePage reports an update on climate change modeling in NewScientist (28 May 2016, paywall):
The bottom line is that low values for the immediate warming in response to a doubling of CO2 can now be ruled out. Similarly, low values for the warming in the decades following a doubling of CO2 can also be ruled out.
In its last report, the Intergovernmental Panel on Climate Change (IPCC) changed its estimate of warming after a doubling of CO2 from between 2 and 4.5 °C to between 1.5 and 4.5 °C, based on studies like Forster’s. This relatively minor change was seized upon by climate-change deniers as proof that the dangers of global warming had been exaggerated.
The next IPCC report will be revised back upwards, Shindell thinks. But the IPCC was right to lower it when it did, he says: its reports have to be based on the evidence available at the time.
While we can now rule out low estimates of climate sensitivity, Shindell says, we can’t rule out high estimates. “There’s a long tail of very high sensitivity that should dominate our thinking,” he says. When we buy house insurance, we take the worst-case scenarios – fires and floods – into account, Shindell points out. With climate change, we should also act based on the worst case scenarios.
MIT’s latest report on Climate Change, ENERGY & CLIMATE OUTLOOK PERSPECTIVES FROM 2015:
With emissions stable and falling in Developed countries, on the assumption that the Paris pledges made at COP21 are met and retained in the post-2030 period, future emissions growth will come from the Other G20 and developing countries.
Growth in global emissions results in 64 gigatons (Gt) CO2-eq emissions in 2050, rising to 78 Gt by 2100 (a 63% increase in emissions relative to 2010). By 2050 the Developed countries account for about 15% of global emissions, down from 30% in 2010.
CO2 emissions from fossil fuels remain the largest source of GHGs, but other greenhouse gas emissions and non-fossil energy sources of CO2 account for almost 1/3 of total global GHG emissions by 2100, slightly down from the 35% in 2010.
Emissions from electricity and transportation will together account for about 51% of global CO2 emissions from fossil fuel use in 2050, decreasing slightly from the 56% in 2010.
Energy from fossil fuels continues to account for about 75% of primary energy by 2050, despite rapid growth in renewables and nuclear, in part because the natural gas share of primary energy also increases.
The Intergovernmental Panel on Climate Change (IPCC) contributes this time series on CO2 advancement.
Meanwhile, at Mauna Koa’s NOAA station:
The march upward continues.
