Extreme weather events of 2015: Is climate change to blame?

Record temperatures, heatwaves and a brewing El Nino are making this year one of the more unusual in recent history

Composite image of tropical cyclones Nineteen, Nathan and Pam, generated at 09:00 UTC on 11 March 2015 (Pic: NASA)

Composite image of tropical cyclones Nineteen, Nathan and Pam, generated at 09:00 UTC on 11 March 2015 (Pic: NASA)

By Freya Palmer

The past months have witnessed a deluge of extreme weather events and new records.

July 2015 was the warmest month ever recorded for the globe, according to the National Oceanic and Atmospheric Administration (NOAA).

From heatwaves across Europe, the Middle East and South Asia, to flooding in the US and Africa, many observers have been quick to blame climate change.

However, with a brewing El Nino in the Pacific bound to generate a peak in weather extremes, to what extent can we accurately say climate change has had a hand?


According to NOAA, any reliable assessment must allow for a “lag-time”, in order for all relevant factors to be taken into account.

Others take a different view.

Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research said there is scope for assumption, even at an early stage.

And while it is difficult to attribute any single weather event to climate change, long term data provides a basis for assessing the likelihood of the link.

This is possible even during a period of El Nino, he said. While the El Nino will generate a “one-off spike” in meteorological data, more long term trends point to climate change.

Cyclone Pam

In March, category five tropical storm Cyclone Pam hit islands in the South Pacific.

Most of the devastation occurred in Vanuatu but extended to surrounding islands such as Kiribati, the Solomon Islands and Tuvalu.

According to Professor Kevin Trenberth of the US National Centre for Atmospheric Research, the strength of the storm can be explained by the abnormally high sea surface temperatures around Vanuatu – 1-2C higher than average.

“[A]bout 0.6 degrees Celsius can be blamed on human-induced global warming and that means over one degree is ‘natural’ and associated with a weak El Nino.”

Alaska’s warmest May

Temperatures in Alaska were 8.1F (4.5C) higher than average in May, making it the warmest May on record.

This map shows the record heat northwestern Canada and parts of Alaska experienced in the third week of May. (Photo credit: NASA Earth Observatory)

This map shows the record heat northwestern Canada and parts of Alaska experienced in the third week of May. (Photo credit: NASA Earth Observatory)

A report by the US Global Change Research Program shows that over the past 50 years, Alaska has warmed at more than twice the rate of the rest of the US, with an average temperature increase of 3.4F (1.9C).

Texas and Oklahoma

Oklahoma and Texas were hit by record flash floods this May, after each experienced their wettest months on record. At least 31 people were killed.

According to Tom Di Liberto, a meteorologist at NOAA, storms and heavy rain are normal at this time of the year. “That’s springtime,” he said.

Still, while Di Liberto maintained that the role of climate change in these events is uncertain as yet, he did note that there has been an observed change in heavy precipitation across the US.

India’s record heatwave

In May, India was hit by its second deadliest heatwave on record, and the fifth deadliest in world history, with 2,500 killed.

Intense heat in India caused some roads to melt (Pic: GeoBeats News/Screengrab)

Intense heat in India caused some roads to melt (Pic: GeoBeats News/Screengrab)

According to the National Disaster Management Authority of India, ‘Higher daily peak temperatures and longer, more intense heat waves are becomingly increasingly frequent globally due to climate change’

Pakistan’s deadly heatwave

Hit with temperatures as high as 49C, Pakistan witnessed the deaths of 2,000 of its citizens in June, mostly in the Sindh province and its capital Karachi.

Dr Rasul, Director General of Pakistan’s Meteorological Department, told RTCC: “I believe there are links to climate change.

“If we look at the history of heat waves, we can’t find such a prolonged case in that region.”

Europe’s heatwave

In July, temperatures soared throughout Western Europe.

Germany experienced its hottest day since records began whilst in France, thousands lost power as high temperatures causing electrical equipment to malfunction.

Professor Rahmstorf of the Potsdam Institute told RTCC: “There is clearly a systematic increase in heat extremes and the logical cause is global warming.”

When asked whether this year’s heat could be the result of the current El Nino, he said: “If we look at temperatures between 1950 and 1980, there is nothing close to the extreme heat of today, regardless of El Nino, so the effect of global warming is larger.”

Iran and Iraq heatwaves

Bearing the brunt of the Middle Eastern heatwave, parts of Iraq exceeded 50C in August. In response, the government called a four-day holiday.

Meanwhile, in Iran, temperatures exceeded 48C for 7 consecutive days. Coupled with high humidity, this resulted in a heat index of 73C in some parts.

When asked about the heatwaves in Iran and Iraq, Dr Karsten Haustein of the Environmental Change Institute in Oxford old RTCC: “What used to be a 1 in 50-100 year event is a 1 in 5 year event now.

“Hence longer lasting heatwave events have become 10-20 times more likely. It goes without saying that this change is due to human influences on the climate.”

Ghana’s floods

After prolonged heavy rainfall in June, Ghana’s capital city Accra flooded, killing 25 directly and 200 through a petrol station explosion.

Dr David Rain, director of the environmental studies programme at George Washington University, told RTCC that though flooding in Ghana has increased, this is due to population increase and a rise in impervious surfaces like roads and roofs, as opposed to climate change.


The self-styled Sunshine State is facing its most severe drought in a millennium. A State of Emergency has been called, sanctioning all necessary actions in preparation for water shortages.

When asked for comment by RTCC, experts at NOAA said it is too early to attribute California’s drought to climate change but directed us to an earlier report on the Californian droughts of 2013 and 2014.

This pointed to warm sea surface temperatures (caused by anthropogenic greenhouse gases) as a large factor in the probability of 21st century California droughts.

This week a study in the journal Geophysical Research Letters said human-induced climate change was intensifying the drought.

“A lot of people think that the amount of rain that falls out the sky is the only thing that matters,” said lead author Alton Williams, bioclimatologist at Columbia University.

“But warming changes the baseline amount of water that’s available to us, because it sends water back into the sky.”

Myanmar Flooding

Myanmar recently experienced its worst flooding in decades, with over one million “critically affected” according to the UN Office for the Coordination of Human Affairs.

(Pic: ActionAid/Flickr)

(Pic: ActionAid/Flickr)

“The recent floods in the region due to heavy monsoon rains, including the devastations we are currently witnessing in Myanmar are a grim reminder of the consequences of climate change and it is the poorest and most marginalized who are affected the most,” said Toily Kurbanov, UNDP Country Director

However, according to Dr Martin Beniston of the University of Geneva, the flooding “is probably more linked to the El Nino effect, which is this year particularly strong and usually upsets weather characteristics around the Pacific Rim and Indian Ocean”.

Brazilian drought

Brazil is experiencing its worst drought in 80 years. During its rainy season earlier this year, rainfall was 8 inches (20cm) lower than average.

According to a study published by the National Academy of Sciences, the southeast Amazon has dried by 25% since 2000.

Research points to deforestation as the major driver of drought in Brazil, as Dr Antonio Nobre from the National Institute for Atmospheric Research explains.

“The forests have an innate ability to import moisture, and to cool down and moisten the air and favour rain,” he said.

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