Climate change is one of the biggest challenges facing our world, responsible for an increase in extreme weather events such as heatwaves, hurricanes and drought.

Orange markers denote human influence on extreme weather Image: Carbon Brief

To help us understand the effects of human activity on the climate, the website Carbon Brief has created an interactive map using information from over 140 peer-reviewed articles from the last 20 years that explore extreme weather events and their causes.

2015 had the most recorded extreme weather events. Image: Carbon Brief

The data shows 63% of extreme weather events studied were made more likely or more severe by human-caused climate change.

In 32% of cases, the evidence was either inconclusive or there was no discernible human influence.

Interestingly, 5% of studies revealed human activity actually made extreme weather events less likely or less severe. Carbon Brief points out that this data set includes blizzards and cold snaps.

Rising temperatures make certain weather events more likely to occur. Image: Carbon Brief

The research, which Carbon Brief will update periodically, is focused primarily on heatwaves, drought and heavy rainfall and flooding, with around a quarter of all studies taken from extreme weather events in Australia.

Heatwaves

Of the 48 heatwaves studied, a staggering 85% were found to have been made more likely to occur or more severe as a result of climate change. In one example, which studied the Korean heatwave in 2013, the extreme weather was found to be 10 times more common because of climate change.

However in one other case – an analysis of the Russian heatwave in 2010 – climate change was not found to be a contributing factor.

Heavy rain and flooding

Just under half (45%) of the 29 studies showed that heavy rain and flooding were adversely affected by climate change, the research shows.

Twenty-eight percent of studies found no evidence, while 24% were inconclusive. Just one study, relating to prolonged heavy rainfall in Colorado, found climate change made the event less likely to occur.

In response, Carbon Brief says: “It’s also important to stress that the absence of evidence for a link to climate change isn’t the same as evidence of absence. This is why a single study should never be considered the final word on how climate change influences a given type of extreme weather.”

Drought

Of the 33 studies that analysed drought, 58% were found to be exacerbated by climate change, while 24% were inconclusive and 15% found no discernible link.

However, Carbon Brief says droughts are a complex weather event to analyse, adding that conclusions about the role of climate change in a specific drought “could depend on whether a study looks at temperature, precipitation or soil moisture, for example”.

Climate change makes heat and drought more severe or more likely to occur. Image: Carbon Brief

More broadly, Carbon Brief also says it is important to understand that finding climate change contributed to an event is not the same as saying it caused that event.

Paris Agreement

The threat of climate change led to almost 200 nations signing the Paris Agreement in 2015, although the United States, one of the world’s largest polluters, decided to pull out of the accord last year.