Extreme weather is on the rise

From record-breaking heatwaves and wildfires to disastrous floods, human-caused climate change is devastating our planet. And it will get worse...

Rescuers with a boat and wading through the water of a flooded street in the middle of York city buildings

We have produced world-leading research proving that human-caused climate change has changed both the frequency and severity of extreme weather events.

Human-caused climate change is causing extreme weather such as heatwaves, heavy downpours, droughts and hurricanes all over the planet.
Further global heating is intensifying these devastating extremes and will make them even worse in the coming decades.
Even if we make drastic reductions, we will not return the world to the more moderate weather of the past.

So, what is happening?

You can find out key information by clicking on each heading below:

Latest observations - humans are causing devastating extremes

A photo showing several people's legs wearing wellington boots as they wade through floodwaters

Our research evaluated climate variability and attributed causes to changes in tropical and subtropical rainfall.

We have shown that human emissions have contributed to observed changes in large-scale precipitation. The frequency and intensity of heavy precipitation events have increased over most land areas. Since 1950, global precipitation has increased, but while some regions have become wetter, others have become drier as anticipated from our modelling. We also accounted for those regions shifting, and our findings were reflected in our figures that were used in the latest report.

The new report reflects major advances in the science of attribution - understanding the role of climate change in intensifying specific weather and climate events.

It shows how and why the climate has changed to date and the improved understanding of human influence on a wider range of climate characteristics, including extreme weather.

Here are a couple of differences:

Topic	Fifth Assessment Report (AR5) 2013/14	Sixth Assessment Report (AR6) 2021
Precipitation	Confidence in precipitation change averaged over global land areas since 1901 is low prior to 1951 and medium afterwards.	Globally averaged precipitation over land has likely increased since 1950, with a faster rate of increase since the 1980s (medium confidence).
Precipitation	Anthropogenic influences have contributed…to intensification of heavy precipitation over land regions where data are sufficient (medium confidence).	Human-induced climate change is likely the main driver [of observed increases in heavy precipitation events].
Precipitation	Anthropogenic influences have contributed…to global-scale changes in precipitation patterns over land (medium confidence).	It is likely that human influence contributed to the pattern of observed precipitation changes [over land] since the mid-20th century.
Precipitation	There are likely more land regions where the number of heavy precipitation events has increased than where it has decreased.	The frequency and intensity of heavy precipitation events have increased since the 1950s (high confidence).
Heat extremes	It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale. It is likely that the frequency of heatwaves has increased in large parts of Europe, Asia and Australia.	It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s, while cold extremes (including cold waves) have become less frequent and less severe.
Heat extremes	It is now very likely that human influence has contributed to observed global scale changes in the frequency and intensity of daily temperature extremes since the mid-20th century, and likely that human influence has more than doubled the probability of occurrence of heatwaves in some locations.	[There is] high confidence that human-induced climate change is the main driver of these changes [in heat extremes]. Some recent hot extremes observed over the past decade would have been extremely unlikely to occur without human influence on the climate system.
Drought	The frequency and intensity of drought has likely increased in the Mediterranean and West Africa [since 1950], and likely decreased in central North America and north-west Australia. [Assessment of a human contribution]: (Low confidence.)	Human-induced climate change has contributed to increases in agricultural and ecological droughts in some regions due to increased land evapotranspiration (medium confidence).
Troposphere	It is very likely that anthropogenic influence, particularly greenhouse gases and stratospheric ozone depletion, has led to a detectable observed pattern of tropospheric warming and a corresponding cooling in the lower stratosphere since 1961.	It is very likely that well-mixed greenhouse gases were the main driver of tropospheric warming since 1979.

What of the future? Extreme weather events will get even worse

Three cows standing on the patio of a house surrounded by floodwaters

AR6 used a combination of historical observations, climate models and an update of climate sensitivity to provide the best estimate that the world might pass the 1.5C and 2C global warming levels.

Every fraction of a degree of further heating causes clear increases in the intensity and frequency of heatwaves, heavy rainfall, droughts and extreme weather events.

It found that within the next two decades, temperatures are likely to rise by more than 1.5C above pre-industrial levels, bringing widespread devastation and extreme weather.

The results of AR6 are clear

Drastic reductions in emissions can stave off worse climate change. Still, they will not return the world to the more moderate weather patterns of the past.

Even if we can stabilise the climate at 1.5C, the level of heating will still result in increasing heatwaves, more intense storms and more serious droughts and floods.

Here are a couple of notable differences:

Topic	Fifth Assessment Report (AR5) 2013/14	Sixth Assessment Report (AR6) 2021
Precipitation	Extreme precipitation events over most of the mid-latitude land masses and over wet tropical regions will very likely become more intense and more frequent by the end of this century, as global mean surface temperature increases.	It is very likely that heavy precipitation events will intensify and become more frequent in most regions with additional global warming. At the global scale, extreme daily precipitation events are projected to intensify by about 7% for each 1C of global warming (high confidence).
Precipitation	Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.	There is strengthened evidence since AR5 that the global water cycle will continue to intensify as global temperatures rise (high confidence), with precipitation and surface water flows projected to become more variable over most land regions within seasons (high confidence) and from year to year (medium confidence).
Heat extremes	It is virtually certain that there will be more frequent hot and fewer cold temperature extremes over most land areas on daily and seasonal timescales as global mean temperatures increase. It is very likely that heat waves will occur with a higher frequency and duration.	Every additional 0.5C of global warming causes clearly discernible increases in the intensity and frequency of hot extremes, including heatwaves (very likely).
Drought	Increases in intensity and/or duration of drought: Low confidence [for the early 21st century]; and likely (medium confidence) on a regional to global scale [for the late 21st century].	Discernible changes in intensity and frequency of meteorological droughts, with more regions showing increases than decreases, are seen in some regions for every additional 0.5C of global warming (medium confidence). Increases in frequency and intensity of hydrological droughts become larger with increasing global warming in some regions (medium confidence).
Monsoons	Globally, it is likely that the area encompassed by monsoon systems will increase over the 21st century. While monsoon winds are likely to weaken, monsoon precipitation is likely to intensify due to the increase in atmospheric moisture.	Monsoon precipitation is projected to increase in the mid- to long term at global scale, particularly over south and south-east Asia, east Asia and west Africa apart from the far west Sahel (high confidence). The monsoon season is projected to have a delayed onset over North and South America and West Africa (high confidence) and a delayed retreat over west Africa (medium confidence).

Our research on extreme weather

Hurricane typhoon over planet Earth viewed from space. Elements of image are furnished by NASA.

We have produced world-leading research into validating the hypothesis that human-caused climate change has changed both the frequency and severity of extreme weather events.

Our work has shown that human emissions have contributed to observed changes in large-scale precipitation.

In addition, we have led the interpretation of results that found increases in emissions of greenhouse gasses have caused a 5% increase in extreme precipitation events across the globe.

Professor Gabi Hegerl has written guidance notes for attribution of change in physical climate and impacts such as ecosystem and agricultural changes. These were used by the previous IPCC assessment (AR5) and are still being used today.

Latest research

For the IPCC Sixth Assessment, our work evaluated climate variability and attributed causes to changes in weather events. Various works from our researchers were cited throughout, plus several figures were used by the AR6 report.

Dr Andrew Schurer was selected as a Contributing Author for 'Chapter 3: Human influence on the climate system'. He was responsible for providing text and expert opinion about the climate of the last millennium. This included a figure which demonstrates the detection of human influence on large scale precipitation patterns over the tropics
Professor Gabi Hegerl was specifically selected as an Expert Reviewer for the report and was involved in discussions across the IPCC Working Groups on attributing causes to observed changes.

Our work with the IPCC

What are we doing about climate change? Our impact on IPCC	Our work on the IPCC (AR5) report - the foundation for the Paris Agreement
What is the IPCC? And why should we trust it?

It confirms impressively to what extent we are already experiencing changes in extreme weather and climate extremes, from heat waves to heavy rainfall to drought. Unless we transition to net zero, we will see increasingly more damaging events.
Professor Gabi Hegerl
School of GeoSciences

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What is the IPCC, and how has our research helped?

We've provided more information on our work and the role of the IPCC:

What are we doing about climate change? Our impact on IPCC	IPCC Special Report 'Global Warming of 1.5 Degrees C
What is the IPCC? And why should we trust it?	Our work on the IPCC (AR5) report - the foundation for the Paris Agreement

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This article was published on 2024-07-01