2014 likely to be the warmest year ever recorded

To assess the potential link between Europe’s likely record-breaking hottest year and global warming, Climate Central worked with scientists from the Royal Netherlands Meteorological Institute (KNMI), the University of Oxford, the University of Melbourne and the Australian National University. The three teams conducted independent assessments, using different approaches involving statistical analyses of the historical temperature record and the results of thousands of simulations with state-of-the-art climate models.

The KNMI and Melbourne teams found that the odds of average temperatures across Europe reaching this year’s record-setting levels were increased by at least 35 to 80 times due to human influence on our climate. The team at the University of Oxford found that, even on a more local scale where variability is often greater, global warming had increased the odds of a year as hot as the one just experienced in most of continental Europe by at least a factor of 10.

Hot years are getting hotter

Climate change makes hot years hotter and more common. Nine of the 10 hottest years ever recorded globally have occurred since 2000. According to NOAA’s National Climatic Data Center (NCDC) there hasn’t been an annual cold record globally since 1911.

In Europe, nine of the 10 hottest years ever recorded have also all occurred since 2000. There hasn’t been an annual cold record across Europe since 1956.

Using early instrumental records and proxies like tree rings to extend the temperature record for Europe back to 1500, climate scientists found that the average January-through-December temperature in Europe during 2014 was very likely warmer than at any time during the past 500 years. Initial estimates from KNMI forecast the January-December annual mean temperature for Europe to be 10.5ºC, or 0.3ºC above the previous record set in 2007.

“In the early 1900s, before global warming played a significant role in our climate, the chances of getting a year as warm as 2014 were less than 1-in-10,000. In fact, the number is so low that we could not compute it with confidence,” Geert Jan van Oldenborgh, a climate scientist at KNMI.

The analysis by van Oldenborgh concluded that global warming has made a temperature anomaly like the one observed in 2014 in Europe at least 80 times more likely. For many individual countries the probability has increased by at least a factor of 30 (e.g., the UK, many countries in Central Europe).

Using a large computing network (weather@home), Oxford scientists simulated possible European weather based on the observed global ocean temperatures. At the same time, they also simulated a 2014 where there is no human-influenced climate change. Comparing those two “worlds” they found that the 2014 European temperatures were much more likely in the world with climate change than the one without.

“It is important to highlight that Oxford’s result crucially depends on the 2014 global ocean temperatures. The same study using 2000-2011 conditions gives a different result although the anthropogenic warming is the roughly same in these years,” said Fredi Otto, a climate scientist at the University of Oxford. “When looking at smaller regions in Europe, we notice that there is a higher variability of temperatures,” Karsten Haustein, a colleague of Otto who conducted the analysis, said. “For example, in central Europe we found that the probability of reaching the observed 2014 temperatures is about 40 times higher. In an even smaller region such as the UK, we found that the probability has increased by a factor of about 10.”

The analysis from climate scientists at the University of Melbourne and the Australian National University showed similar results. Their approach utilised the Coupled Model Intercomparison Project phase 5 (CMIP5) experiments.” By comparing climate model simulations representing the world as it is with simulations of a world without humans, we show that the risk of warm years like 2014 occurring has very likely increased by at least 35-fold,” said Andrew King, a climate scientist from the University of Melbourne who conducted the analysis. “This means that human-induced climate change has very likely played a significant role in 2014 being a record hot year for Europe.”

Nineteen European countries are very likely to see their hottest year on record: