Consequently, much of the concern around global warming is focused on associated effects, such as the melting of glaciers, sea-level rise, floods, droughts, hurricanes, an increase in the frequency and severity of the El Niño – Southern Oscillation (ENSO), and possible abrupt climate changes, such as the shut-down of the thermohaline circulation (MOC) which brings warm waters and mild climates to northern Europe.
The supposed simultaneous increase in floods and droughts has always seemed a bit illogical to me, but the melting of glaciers and the resulting increase in sea-levels seem obvious, and since hurricanes form over warm waters, an increase in those might also be suspected. Since El Niño events are associated with unusually warm waters in the east Pacific ocean, these might also increase in either frequency or intensity, whereas one might suspect less La Niña events (cooling of the east Pacific). Finally, the MOC is driven partly by salinity and temperature differentials, so it is conceivable that a large release of cold freshwater (from melting Greenland ice, for example) could interfere with the functioning of the MOC.
But what do climate scientists have to say about the likelihood, extent and timing of these expected events?
The Fourth Assessment Report (AR4) from the Intergovernmental Panel on Climate Change (IPCC) published last year provides a comprehensive overview of peer-reviewed scientific research on the topic, and summarizes the results in a language that is pretty much understandable to non-climate scientists (1). Chapter 10 from Working Group 1 is titled “Global Climate Projections” and is therefore a central chapter if you want to know what to expect for the rest of the century in terms of climate.
Here are a few interesting excerpts from the Executive Summary of Chapter 10:
“General Circulation Models indicate that the Antarctic Ice Sheet will receive increased snowfall without experiencing substantial surface melting, thus gaining mass and contributing negatively to sea level.” (p. 751)
“Most recent published modelling studies investigating tropical storm frequency simulate a decrease in the overall number of storms.” (p. 751)
“Model projections show fewer mid-latitude storms averaged over each hemisphere.” (p. 751)
“There is no consistent indication at this time of discernible changes in projected ENSO amplitude or frequency in the 21st century.” (p. 751)
“It is very unlikely that the MOC will undergo a large abrupt transition during the course of the 21st century.” (p. 752)
Contrast that to Al Gore’s statement in his 2006 book An Inconvenient Truth: “Our ability to live is what is at stake.” Or James Lovelock in the Daily Telegraph in 2006: “Billions will die…Human civilisation will be reduced to a broken rabble ruled by brutal warlords, and the plague-ridden remainder of the species will flee the cracked and broken earth to the Arctic, the last temperate spot, where a few breeding couples will survive.”
One can’t help wondering if they are even talking about the same planet.
How actually alarming is climate change? Leave your thoughts below.
Lykke Andersen is the Director of the Center for Economic and Environmental Modeling and Analysis (CEEMA) at INESAD
(1) Fourth Assessment Report of the Intergovernmental Panel on Climate Change. See www.ipcc.ch.