22 September 2013

The Real Uncertainties In Climate Change

Posted by Dan Satterfield

The Intergovernmental Panel on Climate Change (IPCC) will release its 5th assessment report next Friday in Sweden. It’s the work of over 200 scientists, who have put together a summary of the peer-reviewed science published over the last several years, and it will almost certainly be bad news.

You’re almost certain to hear some very ridiculous things in the coming days by those who fear the consequences of reducing our use of fossil fuels. It amazes me how a deeply held political view can cause someone (with virtually no background in atmospheric physics) to tell every major scientific body on the planet they are wrong. What’s more, they are totally blinded to the fact of how insanely ridiculous they look in doing so.

Someone asked me last week “if these people didn’t drive me crazy”, and I told them that actually it was just the opposite. It’s served as a very valuable lesson to me. A bright red warning that making decisions based on real facts, and being prepared to change any opinion when new information comes in is a rare asset. This ability is perhaps one of the greatest attributes of a science education, because that in itself embodies the scientific method. Remember my favorite (and often repeated) quote by Dr. Neil de Grasse Tyson that “The great thing about science, is that it’s true, whether or not you believe it”.


Ocean temperatures worldwide were the warmest on record for this past summer. NCDC/NOAA.

So here are some of the silliest things you will hear in the coming weeks, and just so you know, they are all ridiculously false. Most of them laughably so.

1. It’s the sun! (We know for certain that it has not caused more than a fraction of the warming.

2. We are still warming up after the ice age! (Temperatures peaked several thousand years ago when humans were living in caves.)

3. The warming has stopped! The planet is cooling! (This is most popular right now because air temperatures have not risen as fast in the last few years as they did in the late 1990’s. Most of the planets heat resides in the oceans, and they are indeed warming. Internal climate oscillations will continue even as greenhouse gases rise. We are getting less daylight everyday now that fall has arrived in the northern hemisphere, but it was warmer today than it’s been all week! The temperature doesn’t drop a little every day as we approach winter. The same is true of our climate.)

UPDATED: 4. The Arctic sea ice is recovering! Australian John Cook of Skeptical Science posted this graph that shows how laughably silly that one is: (I have updated the graphic below with the new one through 2013. It was made by Dana Nuccitelli.

Just updated with 2013 data by Dana Nuccitelli.

Just updated with 2013 data by Dana Nuccitelli.

5. Antarctic ice is increasing! (No, it’s not. The glaciers are melting rapidly from below. Ocean ice has changed little, and while complicated, the reasons are understood well.)

These are just a sampling, and one thing you might notice is that in almost every instance the person repeating them has little or no background in atmospheric science (and in some cases they sit on the science committee in the Congress!). If they do, then you should ask why they have not published their data in a peer-reviewed journal. There are dozens of great blogs about climate science written by those who work in the field. A good example is Real Climate, and John Cook’s Skeptical Science is another one.The leading blog for those who think the IPCC and NASA,NOAA etc. are all wrong is written by someone with virtually no science background at all.

That should tell you something.

The Real Uncertainties

One of the best methods of determining the rate and magnitude of the greenhouse warming is by looking at how the temperature changed in the deep past when greenhouse gases rose and fell. The ice cores from Greenland and Antarctica tell us that our 21st century models are fairly good at estimating the future, and the past. They are not perfect though, and one of the biggest uncertainties is how the physics in clouds will affect the warming. The ice cores tell us that we will warm, but getting ever more accurate predictions requires a better understanding of the radiation physics of clouds. THAT is the biggest uncertainty in climate science. What you will see online (and on some cable news channels) are the silly claims I mentioned above.

Climate Desk flew along on a NASA mission to better understand what is called the “indirect cloud effect”. See their video below:

The Graph below is from the last IPCC report. It shows how all the forcings add up and where the uncertainties are.


From IPCC WG1 AR4.

I leave you with my favorite and most silly reason that climate change isn’t happening.

Carbon Dioxide only makes up 400 parts per million of the air and it’s impossible for such a tiny amount to have an effect on the planet!

The truth: That tiny amount of CO2 keeps the planet about 30C warmer than it would otherwise be. With no greenhouse gases, our planet would be an ice-cube.