|Totten Glacier (Source)|
Sometimes I am quite optimistic that we will stop global warming getting any worse. The costs of renewables are plunging, there is a ferment of new ideas and technology in batteries, and li-ion battery costs are plummeting, and EVs are about to take off in a big way.
Then there are times when I get deeply depressed about it. This piece by the erudite and informative "RobertScribbler" (Robert Marston Fanney) starts with this:
Looking back to a period of time called the Pliocene climate epoch of 2.6 to 5.3 million years ago, we find that atmospheric carbon dioxide levels were somewhat lower than they are at present — ranging from 390 to 400 parts per million. We also find that global temperatures were between 2 to 3 degrees Celsius warmer than 1880s ranges, that glaciers in Antarctica and Greenland were significantly reduced, and that sea levels were about 25 meters (82 feet) higher than they are today.
Given that atmospheric CO2 levels during 2017 will average around 407 parts per million, given that these levels are above those when sea levels were considerably higher than today, and given that these levels of heat trapping gasses are rapidly rising due to continued fossil fuel burning, both the present level of greenhouse gasses in the Earth’s atmosphere and our understanding of past climates should give us substantial cause for concern.
This past week, even more fuel was thrown onto the fire as a paleoclimate-based model study led by Nick Golledge has found that under 400 parts per million CO2 heat forcing during the Pliocene, substantial portions of Antarctica melted over a rather brief period of decades and centuries.
Well, that's depressing enough, right? Sea levels 25 metres/82 feet higher than they are now. Goodbye Holland, Denmark, Belgium, London, New York, Miami, Melbourne, Bangladesh ..... And it's likely to happen much faster than we think.
Even more interesting and depressing were some of his comments in reply to readers' questions:
Carbon hitting the atmosphere has an almost immediate effect equal to about 1/3 potential warming in about a decade timescale. At 492 CO2e constant we are at approx 1.16 C immediate, 2.3 C by 2100, and 4.6 C over the very long term in the higher sensitivity range. This tracking is pretty accurate to present warming rates. Lower sensitivity yields 1.05 C immediate, 2.1 C by 2100 and 4.2 C long term. It’s worth noting that present warming rates include the longer term effect of approximately 350 ppm CO2 and approx 400 ppm CO2e (which would push present warming higher) and aerosol negative feedback which knocks off the effect of about 30 to 50 ppm CO2e (which keeps present warming cooler). In any case, we’re in the ballpark at 1 to 1.2 C above 1880s values.
Avoiding 2 C is predicated, in my view, on a substantial portion of CH4 falling out after considerable reduction in fossil fuel use. Given the size of the global gas infrastructure, this is certainly possible with rapid cuts to those systems coincident with other emissions cuts as well. For example, you could lose about 30 to 40 ppm CO2e from methane falling out. But it looks like getting to 80 percent emissions reductions by 2050 still puts us on a path for 3 C by 2100 and 6 C over the very long term. We’d have to be far more aggressive with emissions cuts and subsequent atmospheric carbon sequestration to have a shot hitting below 2 C warming this Century. And it’s worth noting that atmospheric carbon capture is likely to be limited to around 1-2 billion tons of carbon drawn down per year as a practical constraint. So we want to make sure Earth System feedbacks do not exceed that range.
In other words, the most pressing and urgent thing we need to do is halt carbon emissions into the atmosphere as swiftly as possible. The next most pressing and urgent matter is trying to gear the human system to draw down carbon. Cuts to zero fossil fuel emissions as fast as possible need to take precedence, however, as that deals with the 11 billion tons per year of carbon that is now hitting the atmosphere. An emission whose vast size would be impossible to deal with using atmospheric capture alone.
It will be tough to avoid 2 C warming by the end of this Century if we do not rapidly cut fossil fuel burning as the [Guardian] article suggests. The 492 CO2e number concerns me quite a bit because it implies 2.1 to 2.3 C warming by the end of this Century. If we get to zero fossil fuel burning by 2040, that still implies about 520 CO2e which perhaps drops back to 480 or 490 as methane falls out. That’s still very close to the mark. It looks to me like we have to both perform that rapid cut and look at atmospheric carbon capture by various means. In any case, these very high CO2e levels are highly unsafe, in my view.
Passing 2 C probably implies about 800 million to 1 billion tons per year of carbon feedback from the Earth System by end Century. That’s about 7-9 percent of the present human emission.
I think in this range we hit a bit of a warming speed bump as glaciers start going down more rapidly and seas begin to really rise. As a result, you’re probably looking at a number of decades and possibly Centuries of very severe storm impacts and very unstable and difficult to predict weather. The ice sheets dumping into the oceans and harming AMOC and other ocean circulation patterns will also tend to disrupt regional and global weather. So it’s here that you get into a period of rapid ocean stratification and extraordinarily bad weather conditions.
I know I’ve said that we are on a path to 4 C under typical warming scenarios, but I think we also need to hold out what happens if ice sheet response becomes quite large.
3 C: Traditional agriculture is going to be taking very hard hits even leading up to 3 C. Post 3 C probably does represent an decline threshold. Adaptation will require very extensive indoor vertical farming on the order of requiring national policy initiatives to support their build-out. Carbon feedbacks do become a bit more of a problem as you start pushing at stores that were laid down more than 5 million years ago. The sea ice and salt water incursion scenarios are in the ballpark.
4 C: You’re probably well past major thresholds for a number of glacier systems. 50 meters of long term sea level rise is probably locked in at this point, although you don’t get all that SLR all at once. Cities at 118 F — well, we have cities out west that are predicted to hit 116 this week. So that’s not too far fetched at all.Wet bulb at 35 C becomes pretty common in a number of regions during hot periods at this threshold. Agricultural collapse pressure is very high. A number of regions including Europe, the U.S. West, China, large parts of Africa, India and many more are all likely to be well outside of growing temperature ranges at this time. Loss of 500 billion tons of carbon from the Arctic at 4 C over 500 years is probably possible at this time. Total annual carbon feedback is probably edging into a range of 1.5 billion tons per year from the Earth System.
[Read more here]
Meanwhile the Right continues to lie about global warming, their useful idiots continue to mouth these lies and argue incoherently that the world isn't warming, politicians (mostly) continue to pretend that they are acting to cut emissions, and ordinary ppl continue to vote for these liars. Global CO2 emissions need to fall by 5% per annum. They've stopped rising, probably, but they're certainly not falling anywhere near fast enough. Deeply depressing.
Because I'm by nature an optimist, and because I believe we--all of us--have our destiny in our hands, in my next post I'll have some suggestions for what you can do to stop this disaster from happening.