In one of Conan Doyle’s Sherlock Holmes mysteries, an apparent theft of a racehorse is solved when Holmes notes “the curious incident of the dog in the night” – the point being that the guard dog for the stable did not bark, showing that the only visitor was known and trusted. In some sense, CO2 is a “guard dog” for oncoming climate change, signaling future global warming when its increases overwhelm the natural Milankovitch and other climate cycles. It is therefore distressing to note that in the last 6 months, the dog has barked very loudly indeed: CO2 in the atmosphere has increased at an unprecedented rate.
And this is occurring in the “nighttime”, i.e., at a time when, by all our measures, CO2 emissions growth should be flat or slowing down. As noted in previous posts, efforts to cut emissions, notably in the EU and China, plus the surge of the solar industry, have seemed to lend credibility to metrics of carbon emissions from various sources that suggest more or less flat global emissions in 2014 and 2015 despite significant global economic and population growth.
What is going on? I have already noted the possibility that a major el Nino event, such as occurred in 1998, can cause a temporary surge in CO2 growth. In 1998, indeed, CO2 growth set a record that was not beaten until last year, but in the two years after 1998, CO2 atmospheric ppm growth fell back sharply to nearly the previous level. By our measures, the el Nino occurring in the first 5 months or so of 2016 was about equal in magnitude to the one in 1998, so one would expect to see a similar short surge. However, we are almost 4 months past the end of this el Nino, and there is very little sign of any major decrease in growth rate. It already appears certain that we cannot dismiss the CO2 surge as a short-term blip.
Recent Developments in CO2 Mauna Loa
In the last few days, I was privileged to watch the video of Prof. John Sterman of MIT, talking about the “what-if” tool he had developed and made available in which climate models drive CO2 emissions growth depending on how aggressive the national targets are for emissions reduction. He was blunt in saying that even the commitments coming out of the Paris meeting are grossly inadequate, but he did show how much more aggressive targets could indeed keep total growth at 2 degrees C. In fact, he was so forthright and well-informed that I could finally hope that MIT’s climate-change legacy would not be the government-crippling misinformation of that narcissistic hack Prof. Lindzen.
However, two of his statements – somewhat true in 2015 but clearly not true at this point in 2016 (the lecture, I believe, was given in the spring of 2016) – stick in my head. First, he said that we are beginning to approach 1.5 degrees C growth in global land temperature. According to the latest figures cited by Joe Romm, the most likely global land temperature for 2015 will be approximately 1.5 degrees C. Second, he said that CO2 (average per year) had reached the 400 ppm level – a statement true at this time last year. As of April-July 2016, however, the average per year has reached between 404 and 405 ppm.
CO2 as measured at the Mauna Loa observatory tends to follow a seasonal cycle, with the peak occurring in April and May, and the trough in September. In the last few years, at all times of the year, growth year-to-year (measured monthly) averaged slightly more than 2 ppm. Note that this was true for both 2014 and most of 2015. Then, around the time that the el Nino arrived, it rose to 3 ppm. But it didn’t stop there: In April, a breathtakingly sharp rise of 4.1 ppm took CO2 up to 408 ppm. And it didn’t stop there: May and June were likewise near 4 ppm, and the resulting total average rise through August has been almost 3.6 ppm. September so far continues to be in the 3.3-3.5 range.
CO2, el Nino, Global Land Temperature: What Causes What?
Let’s add another factoid. Over the last 16 or so months, each month’s global land temperature has set a new record. In fact, July and August (July is typically the hottest month) tied for absolute heat record ever recorded, well ahead of the records set last year.
So here we have three factors: CO2, el Nino, and variations in global land temperature. Clearly, in this heat wave “surge”, the land temperature started spiking first, the full force of el Nino arrived second, and the full surge in CO2 arrived third. On the other hand, we know that atmospheric CO2 is not only a “guard dog”, but also, in James Hansen’s phrase, a “control knob”: in the long term, for large enough variations in CO2 (which can be 10 ppm in some cases), the global land temperature will eventually follow CO2 by rising or falling in proportion. Moreover, it seems likely that el Nino’s short-term effect on CO2 must be primarily by raising the land temperature, which does things like expose black carbon on melting ice for release to the atmosphere, or increase the imbalance between carbon-absorbing forest growth and carbon-emitting forest fires by increasing the incidence of forest fires.
But I think we also have to ask whether the effect of increasing CO2 on global temperatures (land plus sea, this time) begins over a shorter time frame than we thought. The shortest time frame for a CO2 effect suggested by conservative science is perhaps 2000 years, when a spike in CO2 caused Arctic melting indicative of global warming less than a million years ago. Hansen and others, as well, have identified 360 ppm of atmospheric CO2 as the level at which Arctic sea ice melts out, and we only passed that level about 20 years ago – a paper by a Harvard professor projects that Arctic sea ice will melt out at minimum somewhere between 2032 and 2053. In other words, we at least have some indication that CO2 can affect global temperature in 50-100 years or so.
And finally, we have scientific work showing that global land temperature increases that melt Arctic sea and land ice affect albedo (e.g., turn white ice into blue water), which in turn increases sea and land heat absorption and hence temperatures, and these changes “ripple down” to the average temperatures of temperate and subtropical zones. So part of global land temperature increase is caused by – global land temperature increase. It is for these reasons that many scientists feel that climate models underestimate the net effect of a doubling of CO2, and these scientists estimate that rather than 500 ppm leading to a 2 degree C temperature increase, it will lead to a 4 degree C increase.
I would summarize by saying that while it seems we don’t know enough about the relationship between CO2, el Nino, and global land temperature, it does seem likely that today’s CO2 increase is much more than can be explained by el Nino plus land temperature rise, and that the effects of this CO2 spike will be felt sooner than we think.
If the “guard dog” of CO2 in the atmosphere is now barking so loudly, why did we not anticipate this? I still cannot see an adequate explanation that does not include the likelihood that our metrics of our carbon emissions are not capturing an increasing proportion of what we put into the air. That certainly needs looking into.
At the same time, I believe that we need to recognize the possibility that this is not a “developing nations get hit hard, developed ones get by” or “the rich escape the worst effects” story. If things are happening faster than we expect and may result in temperature changes higher than we expect, then it is reasonable to assume that the “trickle-up” effects of climate change may become a flood in the next few decades, as rapid ecosystem, food, and water degradation starts affecting the livability of developed nations and their ability to feed their own reasonably-well-off citizens.
The guard dog barks in the night-time, while we sleep. We have a visitor that is not usual, and should not be trusted or ignored. I urge that we start paying attention.