How climate change affected the world’s weather in 2013

Scientific review shows heatwaves in China, Japan, Korea and Australia were made more likely by global warming

By Megan Darby

Man-made climate change “greatly increased” the risk of extreme heat waves as seen in China, Australia, Korea and Japan last year.

That was the conclusion of a scientific review of 2013’s extreme weather events produced by 92 scientists from 14 countries and published in the Bulletin of the American Meteorological Society.

The role of human activity was less clear in droughts, heavy rainfall and storms.

The report’s authors stressed that did not mean there was no human influence in these events. It simply means that recent analyses could not distinguish it from natural variability.

Here is what the review had to say about extreme weather across eight regions in 2013.

1. California drought

California’s governor declared a state of emergency in January after 2013 turned out to be the state’s driest year on record. Officials brought in water restrictions and prepared for wildfires.

The jury is still out on whether climate change is making this type of drought more likely.

One study found this “exceptional” drought was linked to a large weather system over the northeastern Pacific. This system is expected to come up more frequently under the influence of greenhouse gas emissions.

Other models showed global warming increases air humidity in the northeastern Pacific, cancelling out the effect. The overall risk of drought has not changed since the late 19^th century, according to one reading.

Given the severe impacts of water shortages in a state of 38 million people, lawmakers are not waiting for further research.

They have passed a US$687 million emergency drought relief package with measures to boost resilience, including new wells and pipelines.

2. Australia’s “angry summer”

Dubbed the “angry summer”, Australia’s hot season of 2012/13 saw 123 weather records broken across Australia.

The following summer was even angrier, with the Climate Council reporting 156 records tumbled. The country saw 40C+ temperatures, rainfall lows and large-scale bushfires.

Human influences have made summer heat waves in Australia twice as intense and three times as frequent, scientists found.

Annual average temperatures were at or near record levels across Australia and the western tropical Pacific in 2013.

On this case, the scientists were clear: hot weather on this scale is almost certainly the result of human activity.

Such persistent high temperatures were “either completely outside of, or extremely rare in, the distributions of modelled natural variability”.

This region is part of a bigger picture of rising global temperatures, the review said.

“Although global warming has been described as ‘pausing’ since 2000, global temperatures remain at anomalously high levels, and warm annual and seasonal temperature extremes continue to far outpace the occurrence of cold annual extremes.”

3. New Zealand drought

New Zealand experienced its worst drought in 70 years, which was caused by high pressure weather systems over the summer.

Such pockets of high pressure have been made more likely by climate change, scientists found, although natural variability also played a role.

4. Korea heatwave

It was a bad time for South Korea’s nuclear reactors to be forced offline for safety testing (officials were found to have faked some certificates).

Temperatures hit an all-time high of 39.2C in August 2013 and many people had no air conditioning due to power shortages.

The death rate in Seoul rose 8.4% on the back of the heatwave.

There is more of the same in store, according to the latest study: extremely hot summers in the country have become 10 times more likely as a result of manmade climate change.

5. Japan heatwave

Thousands were hospitalised with heatstroke in Japan that same month.

The mercury reached a national record of 41.0C on the southwestern island of Shikoku.

This was mainly down to natural variability but manmade climate change played “a significant role”, said the scientists.

6. Hot China

The 2013 annual mean temperature in China was the fourth highest since 1961 and 0.6C higher than normal.

July and August were particularly intense, with temperatures exceeding 35C for 31 days straight in Shanghai, the largest city.

The effect of human activities on the climate of central eastern China has been detectable since the early 1990s, according to the scientific review.

Human influence was responsible for around half of the extra heat last summer, it said.

7. Northern India floods

In June 2013, a bout of heavy rainfall over four days wreaked havoc in northern India.

Some 5,700 people were declared missing, presumed dead, in the resulting floods and landslides.

There is some evidence human-induced climate change increased the likelihood of such heavy rain, scientists found.

Limited observational data made it hard to quantify precisely the impact of manmade carbon emissions, they said.

8. European mix

There were record high temperatures across Western Europe in summer 2013, with a seasonal average 1.33C higher than the in the period 1964-93.

Human activities played “a substantial part” in the hot, dry weather, said scientists.

Other parts saw heavy rainfall, causing flooding in the upper Danube and Elbe basins of central Europe. Southern Europe had its second wettest winter since 1948.

The Pyrenees mountains came under a higher than normal volume of snow. Germany and Denmark experienced a violent storm, named “Christian” or “Allan” depending on the country.

Analyses of these events found no evidence climate change had played a hand.

Meanwhile the UK experienced an unusually cold spring, with snowdrifts killing thousands of newborn lambs.

Conditions like this are increasingly rare with manmade climate change, scientists found, becoming 30 times less likely.