The number of deaths caused by flooding has gone down

It has been proven that climate change affects the weather and that global warming has potentially devastating consequences. However, although attribution studies often draw links between extreme weather events and global warming, the data often tells a different story.

After floods like those in Libya, western Germany or Pakistan, attribution studies argued that global warming was likely to be a factor. However: the UN Climate Report did not find any evidence of climate change exacerbating flooding over time. Flooding has not increased – either globally or in these three specific regions. In fact, the number of deaths caused by flooding has gone down significantly, even in poorer countries.

The most important factor in determining whether heavy rainfall leads to flooding is local soil conditions.

Instances of heavy rainfall have become more frequent in many regions in the wake of climate change, according to figures published by the UN’s Intergovernmental Panel on Climate Change (IPCC). However, in Chapter 12 of its most recent progress report, the IPCC said that, on a global level, there was no evidence that human-caused factors had influenced changes in precipitation levels.

Heavy rainfall may be increasing due to global warming – but that does not automatically lead to an increase in flooding, as the WWA acknowledges: the most important factor in determining whether heavy rainfall leads to flooding is local soil conditions.

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Modeling precipitation trends

The contradiction between attribution studies and detection studies, which involve analyzing data over the long term, has long been a concern for climate scientists. They are fundamentally two very different approaches.

In attribution studies, researchers use computer models to simulate the climate in two different worlds: one experiencing human-caused greenhouse gas emissions and one not. They analyze the differences between the two scenarios to determine whether specific weather events are made more likely by climate change. These models have proven reliable for analyzing extreme temperatures directly linked to global warming.

Detection studies are based on decades of weather data

However, researchers have repeatedly found that they can be unreliable when predicting changes to other weather conditions – such as trends in precipitation or attribution studies determining the causes of drought.

By contrast, detection studies are based on decades of weather data: if there is no discernible trend in the specific weather phenomenon being studied, then scientists cannot conclude it has been impacted by global warming. Detection studies are difficult to carry out because by definition the data is limited: extreme weather events are rare – precisely because they are extreme. Therefore it can take a long time for trends to come to light.

When it comes to temperature, both in the sea and on land, the UN Detection Climate Report discovered that climate change had an impact – there has been a significant increase in extreme temperatures. However, the latest IPCC Report did not claim that individual weather events were caused by climate change, unlike the hastily published attribution studies.

Sometimes these studies jump to rash conclusions, such as when Hurricane Florence hit the headlines in Sept. 2018. At the time, a team of researchers claimed that the storm was 80 kilometers larger than it would have been without the impact of climate change, and that it brought 50% more rainfall.

Corrections to false figures aren't reported in the media

One of the scientists involved in the study emphasized that he was trying to estimate the effects of climate change before the storm made landfall. He claimed it was important to publish the findings while the hurricane was still in the news, not months later, when most people are thinking about other issues.

There's a desire to convince the public of the dangers of climate change

A year after the hurricane, the researchers published their analysis in a respected scientific journal. In the study, they wrote that their initial figures were wrong. However, this correction was not widely reported in the media.

It was a similar story with the floods in Pakistan last year. A hastily published attribution study dominated the headlines, claiming that the extreme rainfall was likely exacerbated by climate change. However, most of the media showed little interest in reporting the fact that, after studying the data more closely, scientists found no evidence of global warming having an impact on the monsoon. Instead it was the weather phenomenon El Niño that was found to be mainly responsible for the heavy rainfall.

The UN Climate Report showed that there has been no increase in flooding in Pakistan. In fact, the opposite is true: since 1981, the high-water mark for flooding in most valleys has been lower, according to the progress report. It says that precipitation levels in Pakistan could go down in the future.

These contradictions don’t seem to have put the brakes on attribution reports. In a recent article published in the scientific journal WIREs Climate Change, climate researchers Myanna Lahsen and Jesse Ribot argue that the desire to convince the public of the dangers of climate change is leading scientists and the media to attribute extreme weather events to global warming.

Lahsen and Ribot think there are politics at play here: there are always a number of factors that contribute to weather-related disasters. “Analysts’ choices of analytic frameworks always highlight one cause over others and are thus inherently political, whether or not they recognize this,” the researchers claim.

Political utility

Climate change is “a major problem for humanity," and it is “imperative” to get it under control. However, we are faced with a dilemma: attribution studies seek to highlight the importance of reducing greenhouse gas emissions, while the most effective way to reduce the impact of extreme weather events is to invest in local infrastructure.

“Climate-centric disaster framing is politically useful to actors with interest in diverting attention from local, national and international policy initiatives that might bring – or could have brought – more direct and locally relevant remedial action,” Lahsen and Ribot argue.

Attribution researcher Friederike Otto has also warned of the dangers of overstatement. In an essay co-written with two colleagues and published in the scientific journal Communications Earth & Environment, she wrote: “Stop blaming the climate for disasters.”

She argues that disasters occur when natural dangers combine with high vulnerability of a settlement. “Often people’s social, political and economic status determines the nature of differential and disproportionate impacts,” Otto and her colleagues write. They argue that we must recognize these vulnerabilities in order to reduce the impact of disasters.

Some weather-related disasters are more likely because of human-caused global warming, for example, when they are caused by extreme rainfall, which is more frequent in warmer climates. Natural hazards such as floods become disasters as a result of societal vulnerability, write Otto and her colleagues. This vulnerability is a problem that must be solved on the level of local policy.