Less than 5 percent of people care to know that aerosols cool the planet, I got fired up to write a tutorial about this topic when I read an article in Scientific American, attacking Nick Lewis for writing in his blog that a recently released paper by Bjorn Stevens reinforced the idea that CO2 doesn´t cause as much global warming as claimed by the IPCC. This tutorial also teaches about the quality of the material we can find in famous scientific publications.
Nobel Prize Winner Negishi teaching class
(that´s not me, I´m not Japanese)
The Scientific American piece was a hatchet job, so I decided to prepare my tutorial, write this post, and put a microscopic pinprick back in Scientific America´s hide. In this tutorial I include my own drawings and cartoons about this topic, which you can see below.
To make sure I didn´t put my fingers in my mouth, I reviewed the subject, read a few more papers, consulted a bunch of blogs, and I can confirm I share Lewis and Curry´s updated view of the climate change caused by greenhouse gases.
The story begins with "Rethinking the lower bound on aerosol radiative forcing" , by Bjorn Stevens (Max Planck Institute for Meteorology). It´s followed by Lewis´s very sound comment in his blog, and then Scientific American pisses in the pot publishing “How to Misinterpret Climate Change Research”, with this subheader: “Research into the cooling impact of aerosols sends climate contrarians into a tailspin”.
To explain what this is about, I have prepared my own tutorial in six easy steps:
The NOAA data
First, the temperature record. This the deviation from the average temperature in degrees Centigrade (Americans: please multiply by 9/5ths to get your degrees). I copied a US National and Oceanographic and Atmospheric Administration data set, made a running average to smooth the data a little bit, and copied it over using my Powerpoint pencil.
The NOAA data with my copy, no tricks
Second, I took the copy and moved it away from the original, to show you there´s no trickery involved.
Now comes the hard part. I prepared these cartoons to show you how it works:
Cartoon number 1
Look at Cartoon number 1. Please notice I drew two arrows in the cartoon. The red arrow points up, it symbolizes the CO2 greenhouse effect (CO2 causes warming, OK?). The blue arrow points down, it symbolizes the aerosol cooling effect (if you want to know more about aerosols please go to the bottom of this post). The red arrow is a fatter and bigger, and this is intended to imply CO2 has a large impact. We know that aerosols cause cooling, so we have the blue arrow pushing down on the temperature curve, offsetting the CO2 in part (but not fully, and this is why the temperature increases).
Cartoon number 2
Now look at Cartoon number 2. When Bjorn Stevens comes along as writes his paper, he concludes that aerosols cool a bit less than previously assumed. So now the blue aerosol arrow is smaller. This means aerosol cooling is less powerful. If we keep the CO2 arrow the same size, then it pushes up against a smaller aerosol arrow (the aerosol forcing). And this is supposed to push the temperature line higher (the dashed line is a cartoon showing how the temperature, theoretically speaking, goes up even more if the aerosol effect is weaker).
Cartoon number 3
And look at Cartoon number 3. So, to make things add up we have to shrink the CO2 arrow…this puts the temperature curve back where it´s supposed to be. The need to use a smaller CO2 arrow says CO2 forcing is less than previously stated. Cartoon number 4, below, shows just the arrows.
Cartoon number 4, the same arrows, before and after.
And that´s it for the scientific part of my tutorial.
The “how to shit on humans” lesson is that prestigious publications like Scientific American can blow a gasket, and publish hatchet jobs and garbage.
Appendix. From NASA:
“Whereas aerosols can influence climate by scattering light and changing Earth’s reflectivity, they can also alter the climate via clouds. On a global scale, these aerosol “indirect effects” typically work in opposition to greenhouse gases and cause cooling. While greenhouse gases disperse widely and have a fairly consistent impact from region to region, aerosol effects are less consistent, partly because of how the particles affect clouds.”