Friday January 19th… Dear Diary. The main purpose of this ongoing post will be to track United States extreme or record temperatures related to climate change. I’ll refer to extreme temperatures as ETs (not extraterrestrials)😊. Here is today’s climate change related topic:
Narrowing Global Forecast Ranges
Yesterday we saw that global averages for 2017 ended up third warmest on record about +1.2C above preindustrial levels. The goal of the Paris Accords is to keep averages below +2.0C and optimally below +1.5C. Our best science from the last 25 years predicts a range of +1.5C to +4.5C with not too much hope for remaining below +2.0C. What if we could narrow the forecast ranges? From a policy and political standpoint that would be a big plus. Now a group of researchers has done just that forecasting a range from +2.2C to +3.2C. I’ll refer to this article for today’s topic:
Here are some excerpts from the article:
The metric the researchers used is called equilibrium climate sensitivity, but don’t let the name scare you. “It’s essentially the amount of global warming we would predict if we just doubled the atmospheric carbon dioxide and let the atmosphere and climate come to equilibrium with the carbon dioxide,” says lead author Peter Cox, who studies climate system dynamics at the University of Exeter.
Accordingly, climate scientists have been working to narrow that ECS—or constrain it, in their parlance. “The consequence of it being so large,” says Cox , “is you can have certain camps argue that it could be on the low side, so why do we worry, and other camps worry it’s on the high side, which means there’s a catastrophe coming and there’s nothing we can do about it.”
Now, you can try to constrain ECS by looking at historical warming events. But what Cox and his colleagues did was actually ignore the warming trend to date. “You might imagine the most obvious thing to do to get an idea of future climate change is to look at climate change to date,” says Cox. “But it turns out that’s a really poor constraint on the equilibrium climate sensitivity, and it’s basically because we don’t really know how much extra heat we’ve put in the system.”
Optimism, though: While a study last summer found that humanity had pretty much zero chance of making the 2°C goal, this new constraint could change that outlook. “Paris is more feasible than I thought before I started out on this,” Cox says. “It’s feasible now to avoid 2 degrees, whereas I would have said before that it was pretty much unlikely that you were going to do that.”
Which is useful information, scientifically speaking. But also politically. “I think in some ways the non-scientific message from this is that climate change, or climate sensitivity, is large enough to need action, but not so large that it’s too late to do anything,” Cox says.
As stated at the beginning of doing climate posts last year, I’m interested in the ebbs and flows, or dips and spikes, in climate trend charts, because I believe that those can scientifically tell us something. Evidentially Cox and others think so too. Cox and his group might be in error, though.
Dr. Michael Mann was gracious enough to comment when asked:
“There may be some problems with the methodology that lead to low-biased estimates of climate sensitivity. Relates to issues we discussed in this 2008 JGR article:” http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/FosteretalJGR08.pdf …
BTW December 2017, globally, turned out to be the 3rd warmest December in recorded history:
Temperature percentiles for land and ocean areas across Earth in December 2017, as compared to all Decembers from 1880 to 2017. Areas in darkest red had the warmest monthly temperatures of any December on record. No land or ocean areas experienced record-cold December temperatures. Image credit: NOAA/NCEI.
Synoptically we are seeing a weather patter across the U.S. in which there will be very few ETs, but I will report any I see later today.
The Climate Guy