How can we know when we’re actually feeling climate change and not just another weird summer?

WHO: James Hansen (NASA Goddard Institute for Space Studies, Columbia University Earth Institute)
Makikio Sato (NASA Goddard Institute for Space Studies, Columbia University Earth Institute)
Reto Ruedy (Trinnovium Limited Liabilty Company (a data analysis company that works with NASA))

WHAT: Working out how you can perceive and feel climate change

WHEN: 6 August 2012

WHERE: Proceedings of the National Academy of Sciences (USA), 2012 (109)

TITLE: Perception of Climate Change

Climate vs weather: which one is which? And how can we tell if the extreme weather that’s been occurring around the globe this year is because of climate change? Dr James Hansen, the head of NASA’s Goddard Institute and the guy who has been doing climate models since the 1980s before most people had heard about climate change is here to show us how we can tell our climate dice are loaded and we’re currently playing Russian roulette with our futures.

In quite a readable paper, he looks at average weather data from 1951 through to 2011 and compares them decade by decade. The standard used by the World Meteorological Organisation is that while weather is what you see out your window, climate is 30 years worth of data (because the climate is the long term trends, and you can’t get a trend from today vs tomorrow).

To find a base of ‘normal’ to compare with, they picked 1951-1980 which gives a 30 year period of stable and normal weather that also had detailed records kept across the globe. They then compared it with the next three decades to see how quickly our climate is changing.

Firstly, the base of normal. Stretch your minds back with me to high school statistics and your friend the bell curve (yay!). It’s a great way to show variation across a population – with the majority of people falling into the middle and the outliers to the tails. Same works for weather. The majority of the temperatures day to day fall into the middle and the tails of extreme heat or extreme cold are much rarer.

In a bell curve, the odds of being more than two standard deviations from the average are 2.1% and the incidence of averagely hot or cold summers from 1951-1980 was about 33% (either side of the middle).

Bell curve with standard deviations (signified by σ) from Wikipedia

As we have poured more carbon pollution into the atmosphere further forcing changes in the climate, we’ve pushed that bell curve for summers to the right, meaning there are less cold summers, more hot summers and some extremely hot summers now.

Extremely hot summers are summers that are three standard deviations from the average (ie. extremely rare) that were almost non-existent in the 1950s now occur 10% of the time. Averagely warm summers that used to be 33% of the time are now 75%.

Your summers on climate change – normal, warm, hot, hotter (from paper)

But statistics, numbers, blah. What does this actually mean, or feel like or look like?

Three standard deviation hot summers look like the heat wave in Moscow in 2010. The summer grain harvest was seriously reduced and exports were stopped, more than 500 wildfires burned across Russia, nuclear power plants had to be shut down because they were overheating, 11,000 people died in Moscow alone and the country had the highest temperatures in 1,000 years.

Now, maybe some of you reading haven’t felt temperatures that high consistently in a heat wave before, or if you’re in the Pacific Northwest are thinking that some heat wave might be nice given the crappy summer we’ve had this year. However, I did my final university exam in Melbourne, Australia in 46⁰C heat, and I can tell you it’s not fun. Neither are the permanent water restrictions that come with extended hot and dry weather.

Dr Hansen states in his paper that action won’t be taken on climate change until the public can understand the consequences of climate change and decide that they’re unacceptable. The heat is already on and the wildfires are already starting.

I don’t want this to become the new normal – do you?