2010 Russian Heat Wave - An Alternative Approach

Following this month's earlier post on the same topic, I'd like to have another look at the Russian 2010 heat wave. The previous post focussed mainly on a paper which found that there was no reason to suspect global warming was to blame for the heat wave (Dole et al., 2011). It's worth repeating one of this paper's main findings: "We conclude that the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability".

Scientific consensus?

However, there's a difference of opinion expressed by other climate scientists, who find that there was an increased likelihood of the Russian heat wave of 2010 because of global warming (Rahmstorf and Coumou, 2011). The approach they take is appealing because of its simplicity: they use straightforward arguments based on the statistics of such events and a combination of Monte Carlo simulations and analytical solutions. The conclusions they draw are not hard to understand either: if you assume there is an underlying upward trend in the time series with some random noise added to this then you would expect there to be a higher chance of observing an extreme event towards the end of the time series than if the time series were stationary (i.e. no underlying trend). A simple visual representation of this can be seen in the graph below, which shows the average global (D) and Moscow (E) temperature record over the last 100 years.

Normalised (by the s.d.) temperature records for the Earth (D) and Moscow (E)

Using this line of reasoning they find that there is an 80% chance that the 2010 Russian heat wave was caused by the underlying warming trend, and they point out that "Our results thus explicitly contradict those of Dole et al.".

They also claim that "Fig. 4 clearly shows that the warming trend after 1980 has multiplied the likelihood of a new heat record in Moscow and would have provided a strong reason to expect it before it occurred.". This is again in contrast to the Dole et al. paper, which says that it was unpredictable. I think the resolution of these two points of view is fairly easy though: the ability to predict an event is far tougher than merely expecting that an event might happen.

In a final post on this topic in the new year I'm going to see whether these two different takes on the same event can be reconciled.

EDIT:

The final post is now up, take a look here for the final instalment.

Cool Visualisation of the Earth's wind

Here's a visualisation I just came across showing the current wind speeds and directions across the Earth. According to its about page it shows global weather conditions that are "forecast by supercomputers" and "updated every three hours".  There's more information on the site's github page, the gist of which is that it pulls weather data from the National Centers for Environmental Prediction, NOAA / National Weather Service and displays it in your browser. The map below shows the wind above Britain as it is at the moment (it certainly feels pretty windy up here in Edinburgh!).

Britain on Dec. the 18th

It should work in any modern browser, so go have a look and see what you think. It'd be interesting to see how easy it is to show other types of information, e.g. snow cover, sea ice or global temperatures, using the same infrastructure. One of the key aspects of climate science is communicating results to as wide an audience as possible, and graphically rich interactive tools like this one can only help capture people's imaginations and give them a feel for what the Earth is doing.

CryoSat Turns its Hand to Measuring Storm Surges

The satellite CryoSat's main role is, as its name suggests, to measure sea ice thickness. However, the ESA have been busy repurposing its altimeter so as it can measure sea level, even close to land.  They've used this to measure the European storm surge, and validate some models in the process. It's a taste of what Sentinel-3 will offer us, another satellite that has similar instruments to CryoSat, but is focussed on measuring sea-surface topography.

Dramatic Tidal Surges Hit East Coast of UK

The recent tidal surges that have hit the East Coast highlight a couple of points: namely that the current flood defences that are in place are vital to safeguarding properties, with the authorities saying that over 800,000 properties are said to have been protected, and that predicting how these surges are going to change over the coming decades is equally important for all people that live in the affected area. Predicting how these surges will change will allow for planning of the next generation of sea defences, which will almost certainly be required with the IPCC saying that sea levels are forecast to rise by 26 to 55cm by 2100 (WGI AR5, 2013) - even with the most ambitious cuts in emissions. The effects of the surges can be seen in the following video:

Extreme Weather across the UK

The mild windiness that we had here in London was nothing compared with what was going on up and down the country: http://www.theguardian.com/uk-news/gallery/2013/dec/05/extreme-weather-in-the-uk-in-pictures

2010 Russian Heat Wave

In 2010 large swaths of the earth were hit by extreme weather in the form of heat waves. The effects were particularly strong in Russia, where numerous records for the hottest day across the country were broken (or smashed in some cases). Over 50,000 deaths were reported in Russia (Khandekar et al., 2013), and according to the Guardian, temperatures were around 10C above their seasonal average and there were substantial damages to the wheat harvest, costing the Russian economy $15bn. The cause of the heat wave was a blocking anticyclone over Russia, that was maintained by "anomalous cyclonic conditions over the Mediterranean area" and a similarly anomalously strong monsoon circulation (Trenberth et al., 2012). This blocking high lead to a temperature inversion which trapped exhaust fumes close to the ground, leading to some pretty horrendous conditions in Moscow:

Moscow on the 17th of June and 10th of August

From this it's clear that the human costs of extreme weather can be devastating, even when the extreme weather is not in the form of a one off extreme event such as a hurricane or a flood. The question of attribution of these events is therefore hugely relevant to the debate on climate change, because if it were to be shown that these events were caused by a warming climate, then this would directly link anthropogenic influences to huge economic and human costs.

How can a single event be attributed to a warming climate?

It is notoriously difficult to attribute a single given event to climate change. Indeed, it may well be a futile task, here is part of a paper examining the role climate change had on the 2003 heat wave in Europe (Stott et al, 2005): 

It is an ill-posed question whether the 2003 heatwave was caused, in a simple deterministic sense, by a modification of the external influences on climate—for example, increasing concentrations of greenhouse gases in the atmosphere—because almost any such weather event might have occurred by chance in an unmodified climate.

The paper goes on to examine the link between increased global temperatures and the risk of a given event happening. That is, assuming that there's no direct connection between the event and global warming, rather there's a possibility of increased statistical likelihood that the event was caused by climate change. They find that this was the case for the 2003 heat wave in Europe, through a method of comparing the temperature in 2003 against a number of simulations using the HadCM3 model for the same area and seeing if the value was outside of statistically significant levels.

Was there a greater risk of the 2010 Russian heat wave because of a changed climate?

In this paper: Was there a basis for anticipating the 2010 Russian heat wave? (Dole et al., 2011), the authors find that "the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability". They use a range of techniques to draw this conclusion, using CMIP3 models and also comparing the heat wave temperatures against historical temperatures for the region. Indeed, this provides the main evidence for their conclusion about the attribution of the event to climate change, making it differ slightly in its methodology to Stott et al. (The model simulations were more involved in trying to hindcast the event than as part of the study of attribution.) This means that their approach for attributing 'blame' is mainly empirical in nature, as opposed to the more model orientated methods used in Stott et al.

Conclusion

It's impossible to say that any one event was 'caused' by climate change. However, it is perfectly reasonable to apportion an amount of blame to climate change, as was done by Stott et al. for the European heat wave. Whereas for the Russian heat wave it is "very unlikely that warming attributable to increasing greenhouse gas concentrations contributed substantially to the magnitude of this heat wave". So is it fair to say that the 2010 heat wave had no link to climate change? On the face of this post's evidence, yes, but things aren't always clear cut in science, and in a future post I'm going to have a look at a paper that finds itself in explicit contradiction to the Dole et al. paper, and see if there's any way of resolving this apparent contradiction.

EDIT:

See this post then for the next in the series, and this post for the final instalment.