New research may silence climate change sceptics

Publish date: October 28, 2011

Climate sceptics cling to the fact that it is impossible to tell if a specific freak weather event is a result of manmade climate change or natural variations. However, new research precariously rocks one of their last remaining lifebuoys.

Russia, July 2010: A crippling heatwave engulfs Russia. More than 500 forest fires rage out of control, spewing climate-damaging soot, also known as black carbon, into the air. 700 people perish in the worst heatwave in the history of the country.

This disastrous incident is the back drop to an analysis, which for the first time puts a figure on the extent of the manmade contribution to climate change: There is an 80 percent chance that the 2010 heat wave was caused by climate change. 

Silencing the sceptics

Stefan Rahmstorf and Dim Coumou, scientists at the German Potsdam Institute for Climate Impact Research, applied a new model relying on a so-called Monte Carlo simulation.

“It is a well known mathematical method, which has been in use since the Second World War. However, this is the first time the Monte Carlo model has been used to analyse climate change”, explains climate advisor Svend Søyland at The Bellona Foundation.

“We still cannot prove, or disprove, scientifically that global warming caused a specific extreme weather event. We can only prove that extreme weather events are more frequent and severe than before.  However, this method gives us a more accurate tool to estimate how likely it is that freak weather events are caused by man made climate change,” adds Søyland.

He believes that if the method is put more widely to use in climate research, it might contribute to silencing climate sceptics – as it puts vital pieces into the ever increasing pile of evidence.


Simply put, the Monte Carlo simulation method calculates probability and is particularly useful when there are many factors with inherent uncertainty. It calculates results over and over, each time using a different set of random values.

“If you roll dice only once, it doesn’t tell you anything about probabilities. Roll them 100,000 times, and afterwards I can say, on average, how many times I’ll roll a six,” explains Stefan Rahmstorf to

Rahmstorf and Comou’s “dice” were a simulation made from a century of average July temperatures in Moscow. These provided a baseline temperature trend. Parameters for random variability came from the extent to which each individual July was warmer or cooler than usual.

After running the simulation 100,000 times, “we could see how many times we got an extreme temperature like the one in 2010,” says Rahmstorf. Then the researchers ran a simulation that didn’t include the warming trend, and compared the results.

The method doesn’t consider the causes of climate change, but according to, Rahmstorf and Coumou write that: “given the strong evidence that most of the warming of the past fifty years is anthropogenic, most of the recent extremes in monthly or annual temperature data would probably not have occurred without human influence on climate.” 

Wakeup call

“I am intrigued by the first results, and I am looking forward to what the application of the simulation model can tell us about other historic weather events” says Søyland, adding that it is important to develop more scientific models, which expose the systematic consequences of climate change more accurately.

In Russia, scientists and politicians are divided in two camps when it comes to climate issues. None of them take the threat to heart.

“Most seem to reject the idea of climate change altogether, while the rest welcomes climate change as an opportunity for Arctic shipping routes and intensified oil and gas activities. However, the German scientist’s analysis of last year’s extreme heat and forest fires should be a wakeup call,” says Søyland.


Contact details:

Svend Søyland, climate and energy adviser at The Bellona Foundation
+ 47 48 79 30 or

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