Well, the slick lessons march on. This week we were told how bad humans have upset net natural balance of nature, how CO2 enhances the greenhouse effect and explores those wonderful fingerprints we were promised in week 1.
The most exciting thing about this week was the poll:
Poll Question: What human fingerprint do you think is the most clear indication of human-caused global warming?
The answered are displayed in a nifty ‘word cloud’. My answer of ‘none’ didn’t do too well.
The Carbon Cycle
The first part on the carbon cycle was a bit of ho-hum. I’m not sure anybody contests the view that there’s more CO2 in the atmosphere now than there was in 1958 when it started being measured at Manua Loa in Hawaii.
I’ve always had lots of questions about the measurement of CO2. Here’s a few:
- Why just measure it at Manua Loa? Is is that hard to measure? Does the fact that there are active volcanos in Hawaii influence the readings?
- How was CO2 measured prior to 1958? The partial answer is not all that well. Most measurements are based on three ice cores from Law Dome in Antarctica by Etheridge.
- Is the CO2 concentration the same everywhere in the atmosphere? Does it vary with height? Does it vary with latitude and longitude?
- What’s the uncertainty in CO2 measurement?
This looks like a topic for a future post.
One of the main claims by the lecturer is that CO2 level were unchanged for hundred of thousands of years until wicked humans started burning fossil fuels. The rise didn’t actually start till the 1950s when it actually started being measured. Sort of a coincidence, but I’m reasonably happy to accept that CO2 has increased due to burning of fossil fuels. I just don’t think it matters much.
One interesting point that was highlighted was one I hadn’t really considered before. While humans supposedly put 7.8 GT (Giga tonnes, billions of metric tons) into the atmosphere each year, the wonderful Earth removes 4 GT for us. I was actually told “nature is resisting the increase”. Good old Nature. No physical explanation was offered for this happenstance so I can only assume it’s one of Gaia’s mysteries.
The final part of the carbon cycle lesson dealt with Residence time and Adjustment time. The claim is that man-made CO2 stays in the atmosphere for about 4 years (the residence time) but if we stopped using fossil fuels it would take 50-200 years to get back to ‘normal’ levels. Since I can’t see that happening anytime soon it seems a silly thing to worry about.
I also wondered what happens to the extra 4 GT that Gaia removes each year out of the kindness of her heart? Would she stop?
The Greenhouse Effect
The next lesson dealt with the so called ‘greenhouse’ effect. We’ve all been in a greenhouse or at least a car on a hot day. The Sun beats down, heating up the inside and the heat can’t escape so the temperature goes up. Simple.
Except we’re talking about the atmosphere that doesn’t have a glass cover over it. Greenhouse gasses absorb infrared radiation reflected off the Earth’s surface and re-emit it in all directions so some of it, instead of being sent back out into space, heats up the atmosphere.
If CO2 doubled, the physics says the atmosphere would heat up about one degree Celsius, over a period of hundreds of years if nothing else like cloud cover changed. That’s an interesting scientific idea but nothing to get excite, or spend money, about.
The lesson talks about the CO2, never mentions the projected feedbacks and never mentions the one degree of warming.
It was all pretty vague and really nothing I would bother arguing about too much.
The lesson talked about straw-man myths like CO2 is a trace element so it doesn’t matter.
This was the big one I have had been waiting for. Yet another disappointment. The whole forensic beat-up was based on satellite measurements (CERES) showing an energy imbalance of 0.6 Watts per square meter out of an energy input of 340 Watts per square meter. 0.6 is probably less than the accuracy of the instrument, but I’ll look that up.
The other fingerprints were supposed tiny changes to the differences between day and night temperatures and a slight cooling of the upper atmosphere.
I’ll check these again, but none of them are the least significant to my recollection.
So I waited for week three to particularly learn about the ‘fingerprints’. It was a bit of a disappointment.