“The way we see the problem is the problem.” (Covey)
I don’t get invited to parties very often. That is, in part, because I cultivate aggressively critical thinking. My wife will testify that I am doubter, an annoying skeptic. When I apply myself to global warming, I get called a denier because I do not believe what I am told.
Fear not dear reader: I believe that human beings are increasing the amount of CO2 in the atmosphere. I believe that CO2 is greenhouse gas, and that it is contributing to an increase in our global temperature.
So why do I get called a denier? Because of a few forbidden thoughts:
- China and the USA are unlikely to reduce their use of oil before better energy sources are invented. It seems that global-warming politics has rewarded a few individuals, and justify many international conferences, but little concrete progress has been made. We have never had such high carbon emissions despite a worldwide recession. Perhaps we need more engineering and less politics? (Update 2014: Since I wrote these lines, the USA did reduce their use of oil and coal thanks to increased use of shale gas.)
- While CO2 is a greenhouse gas, water vapor and cloud cover are much more important factor in determining our global temperature:
In round numbers, water vapor accounts for about 50% of Earth’s greenhouse effect, with clouds contributing 25%, CO2 20% (Lacis, et al., 2010)
Many global warming models rely on some kind of feedback effect whereas CO2 increases slightly the temperature which then decreases the cloud cover. Predicting cloud cover might be more difficult than predicting CO2 production. In any case, climate predictions are no joke: it is difficult to get it right.
So how did the global-warming predictions fared in the past? Let us look at the predictions made in 1990: they predicted an increase in temperature of 0.3 °C per decade, with an uncertainty range of 0.2 °C to 0.5 °C per decade.
Under the IPCC Business-as-Usual (Scenario A) emissions of greenhouse gases, a rate of increase of global mean temperature during the next century of about 0.3 °C per decade (with an uncertainty range of 0.2 °C to 0.5 °C per decade), this is greater than that seen over the past 10,000 years. (IPCC report 1990)
Yet less than 0.2 °C of warming per decade was observed. To be blunt, they got it flat wrong. Currently, they are predicting an increase of 0.2 °C per decade from this point forward (see John Baez, 2012).
For the next two decades, a warming of about 0.2 °C per decade is projected for a range of SRES emission scenarios. Even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1 °C per decade would be expected. (IPCC 2007)
Will the predictions pan out this time?
(Update (2014): Here is what the latest (2013) IPCC report states:
The observed global-mean surface temperature (GMST) has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years. Depending on the observational data set, the GMST trend over 1998–2012 is estimated to be around one-third to one-half of the trend over 1951–2012. For example, in HadCRUT4 the trend is 0.04 °C per decade over 1998–2012, compared to 0.11 °C per decade over 1951–2012. (IPCC 2013)
As far as I can tell, they are no longer making any prediction (as of 2014).)
I am not nitpicking. A common way to test one’s understanding is to make predictions and check then against reality. If your predictions do not pan out, then something is wrong in your understanding. It does not matter if there is a wide consensus that you are, ultimately, right. If I am asked to believe that you can predict what will happen 100 years in the future, I would like to see some easier prediction working out first.
- Still. Earth is getting warmer.
How worrisome is an increase of temperatures by 0.2 °C per decade? The Roman Empire thrived under temperatures higher by about 1 °C (+1.05 °C, with respect to the 1951–1980 mean). Thus, it seems we can take some warming without dying off. What about 100 years in the future?
Well, before we worry about what the predictions say about 100 years in the future, remember that the climate predictions from 1990 did not pan out.
- Still. Clearly, there is a limit to how much warming the Earth can take.
Even if we were to adopt alternative energies in 50 years, decades of CO2 production might still kill us.
However, there are alternatives to banning oil production: solar radiation management. We might be able to setup space mirrors or otherwise increasing the reflectivity of our atmosphere. We can also seed the ocean with iron: spreading a tiny quantity of iron in the water creates a bloom of algal bloom which later sinks to the bottom of the sea. Obviously, we cannot hope to both keep pumping CO2 in the atmosphere, and correct for it afterward: this could quickly become economically infeasible. But keep in mind that we will soon run out of cheap oil in any case.
- But won’t we suffer due to poor crops in the near future? Maybe not.
Increasing the amount of CO2 in the atmosphere may increase the production of crops, sometimes very significantly. This is hardly surprising if you know that photosynthesis turns CO2 into plants. Effectively, extra CO2 acts as a fertilizer.
There is a positive effect of CO2 enrichment on yield and water use efficiency. If atmospheric CO2 concentration reaches nearly 600 ppm, wheat and maize yields will increase 38% and 12% and water use efficiencies will improve 40% and 25% respectively, in comparison to those without CO2 fertilization. (…) Under future climate change scenarios, CO2 enriching can effectively alleviate the impact of temperature increase on crop yield. (…) The impact of CO2 fertilization on crops is far more than that of temperature. (Tao et al., 2008)
Yet what did the Intergovernmental Panel on Climate Change state in its 2007 report?
By 2020, in some countries, yields from rain-fed agriculture could be reduced by up to 50%.
What backs this alarming statement?
The origin of this claim was a report written for a Canadian advocacy group by Ali Agoumi, a Moroccan academic who draws part of his current income from advising on how to make applications for “carbon credits”. As his primary sources he cited reports for three North African governments. But none of these remotely supported what he wrote. The nearest any got to providing evidence for his claim was one for the Moroccan government, which said that in serious drought years, cereal yields might be reduced by 50 per cent. The report for the Algerian government, on the other hand, predicted that, on current projections, “agricultural production will more than double by 2020”. (The Telegraph, 2010)
That is bad science.
Summary: Global warming experts have yet to make any real progress in solving global warming. They have a tendency to be alarmist and dogmatic. We will invent new technologies, new crops, new weather control systems. Meanwhile, having more CO2 in the atmosphere, and having a moderate warming period might not be a bad thing.
Update: Though I think we must urgently take charge of our climate, I agree with many of the points raised by Richard Lindzen in a talk that happened after this blog post was published.