The dangers behind averages.

2 degrees has become a familiar figure.  We need to stop the climate getting warmer than an average of 2 degrees to avoid catastrophic climate change.  In fact, as top climate scientist James Hansen says, even 2 degrees is too high.  He says bluntly: “It’s crazy to think that 2 degrees celsius is a safe limit,” (

I would go further, and you don’t need to be a scientist to figure it out: it is crazy using an average figure to drive policy.  I think an average hides too much important data – highs and lows which are more dangerous to us.  By focusing on the average we are ignoring some important truths and therefore risk making bad decisions.

An average of 2°C means just that: you take lots of temperatures all over the world’s surface during the year and then divide it by the number of readings.

The other day temperatures in Iran hit 52°C and with such humidity that it “felt like” 73°C.  These are some of the hottest temperatures ever known to man.

Yet according to Weather Online, in Iran “January is the coldest month, with temperatures from 5°C to 10°C, and August is the hottest month at 20°C to 30°C or more.”  There is an average annual temperature of around 18°C.

This just shows how an average can hide bad news: average temperature of 18°C; say it grows to 20°C.  Sounds nice.  But the trouble is that means over 50 degrees for some days in August.

Why does it matter?

This year research was showed how the hand of climate change is behind the drought of 2006 to 2009 and that is one of the causes of the war which started in 2011: The drought was “one of the worst in modern times”   The arrival of 1.5 million impoverished rural people to the cities added to the social stresses which led to the civil war.  From there came the inflagration we know and the emergence of Islamic State as a regional force.

As a result of that several hundred thousand refugees have arrived in Europe (100,000 have come through Hungary) seeking safety.  This has led to a political crisis in Europe, fed extremism, interrupted trade and caused panicky policy-making.  That’s just Syria.  What about crop failure in Pakistan, India, Iran and Iraq?  What happens when the Himalayas dry out ( and the monsoon fails once or twice?

This highlights two key factors which averages ignore.

First, for many things extremes are much more salient: a very hot summer can destroy crops, even if the autumn and winter are cold.  A wet spring might be irrelevant if there is no rain from June to August.  So it is not interesting what the average temperature rise in the Middle East is.  What is interesting is the changes which affect the thing most at risk – in this case drought and farms.

Second, history is not smooth.  There are sudden events which then lead to other events and then things escalate.  You don’t need a whole year of slightly warmer weather to cause problems.  You need a few days of intolerable heat for people to start doing things which have irrevocable consequences.  A riot, a few deaths in one city can mushroom into regional war – consider the way World War 1 was initiated by a single shot in Sarajevo.  Psychologists recognise that hotter temperatures can cause increased levels of aggression and violence (  When temperatures peak, violence can happen.  Depending on the circumstances, the violence can spread.  The peak, not the average, counts here.

From the example in Syria a period of drought in one limited region can have international repercussions – affecting the human species more than any other!

For this reason, in discussion about climate change, we should not just talk about averages.  They risk hiding far too much critical information.  We should identify some main vulnerable areas (in terms of political geography, vulnerable eco-systems) and consider which weather conditions constitute systemic threats.  We must look beyond immediate effects and consider how local effects can spread across the world.

It is time to stop talking about the benign 2 degrees figure and reveal the malign threats which the average hides.

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1 Response to The dangers behind averages.

  1. Big Al says:

    Instead of relying upon the average [temperature], could the average standard deviation be a better proxy for following a trend?

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