miércoles, 1 de febrero de 2012

Although the mean is important so is the standard deviation.

I just finished reading the latest article by James Hansen.
Perceptions of Climate Change: The New Climate Dice
From Wikipedia:
Hansen is best known for his research in the field of climatology, his testimony on climate change to congressional committees in 1988 that helped raise broad awareness of global warming, and his advocacy of action to avoid dangerous climate change. In recent years, Hansen has become an activist for action to mitigate the effects of climate change, which on a few occasions has led to his arrest.
In this 2012 article he compares the changes in earth temperature with the base period of 1950 to 1981. One of the main arguments is that not only the mean temperature is increasing but that the standard deviation of temperature is also increasing. I believe this is a crucial point that is not stressed enough. Climate Change is not just about some degrees more and milder winters in New York City. Climate Change is about increased climatic variability, less predictability on what will occur in terms of extreme weather hazards.
Although I agree with the argument about the overstatement of the impacts of climate change because of not considering adaptation capacities, we also need to consider that increased variability is likely to have an impact on the frequency and intensity of extreme (and perhaps destructive) weather events such as droughts, floods and heat waves. These events are usually unanticipated and can disrupt the agricultural systems of developing countries (and even developed countries like the Russian wheat crisis last year). Although we might be able to foresee sea surface changes and move accordingly, an extreme hydro-meteorological event that dramatically affects agricultural systems could create major havoc in the short-term (read Somalia here).
The IPCC released a report last year on this subject (Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX)http://www.ipcc.ch/pdf/special-reports/srex/SREX_FD_SPM_final.pdf)
To prepare against this vulnerability NASA is developing an Early Warning Famine System that is expected to prepare countries for these extreme events up to four months in anticipation. http://www.fews.net/Pages/default.aspx
Columbia students from the Climate and Society master are being trained, among other things, to provide anticipated information to countries that rely too much on small-holder agriculture. But a predictive widow of four months is not enough to adapt to climate variability, and our global models lack the resolution to provide with more regional prediction capacity for the long term (decade).
In Hansen’s article there are other interesting aspects to review, for example he shows the regional increase in temperature. This shows that the USA shows a steady temperature pattern, other regions like Europe, China or even Mexico and the Southern USA do show noticeable increases in temperature means in the Summer. No wonder why the reaction to Climate Change is lower in the USA than in other countries. But heat waves in Texas might start to change this behavior.
A final interesting aspect from the article is a discussion on the reasons to fix 1950-1981 as the base years for the analysis. Hansen analyzes how the data looks when taking different base periods. In his own words:
“Because climate variability increased in recent decades, and thus the standard deviation increased, if we use the most recent decades as base period we "divide out" the increased variability. Thus the distribution function using 1981-2010 as the base period does not expose the change toward increased climate variability.
Reports of climate anomalies to the public often use the most recent three decades, prior to the current decade, to define "normal" climate, i.e., to define the base period.
However, this practice tends to hide the fact that climate variability itself is changing on decadal time scales. Thus, at least for research purposes, we recommend keeping the base period fixed.
Global temperature in 1951-1980, which is the earliest period with good global coverage of meteorological stations, is more representative of the Holocene and the climate to which plant and animal life on the planet is adapted.”
I suppose that the debates about science of climate change are not just caused by the uncertainties but also due to its complexities. The long-term nature of the issue, the regional variability of the changes and especially the non-linearity of the Earth’s system are the reasons why most people outside of the scientific community struggles to understand what is actually true, what is not and what is just uncertain. The Center for Research on Environmental Decisions at Columbia University released a fantastic guide for journalists and educators to understand how to explain Climate Change. The guide is called: The Psychology of Climate Change Communication and can be found here: http://cred.columbia.edu/guide/
A long post that I hope you will enjoy.

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