Climate change and extreme events

During February, we saw a series of extreme weather events globally, and Professor Stephen Belcher and Professor Jason Lowe OBE wrote a blog post about preparing the scientific response to growing climate challenges.

So it’s as timely as ever that this month we take a closer look at extreme events, particularly droughts, heat, wildfires, and rains/floods. In fact, one of the five Reasons for Concern (RFC) identified by the Intergovernmental Panel on Climate Change (IPCC) is the risk posed by extreme events. In this blog post, Professor Peter Stott, Science Fellow in Climate Attribution at the Met Office Hadley Centre, will explore the changes in extreme events that we are already seeing around the world.

Climate change attribution

To determine whether a particular weather event has become more severe or more likely due to climate change, attribution studies use computer model simulations of the climate. One of these sets of simulations represents the current climate, including anthropogenic (human-induced) climate change, while the other set of simulations represents the natural climate where the influence of increasing greenhouse gas concentrations has been removed. and other human factors. Comparing the results of the two sets of simulations allows us to assess the level to which climate change has affected the climate.

Rainfall and floods

In the last week of February, parts of the UK experienced significant flooding following a series of storms, a reminder of the impact the weather can have on lives and livelihoods. At the same time, communities in Australia have experienced devastating flooding and several people have tragically lost their lives.

Analysis is needed to determine whether these specific events were more likely due to anthropogenic climate change, but trends in climate data indicate that there have been increases in extreme precipitation globally since the early 20th century; we explored this in a blog post earlier this year. There is also a large body of evidence that has found links to climate change after a series of specific heavy rain events.

An attribution analysis of the UK’s wettest February on record (occurring in 2020) showed that experienced rainfall extremes were three times more likely due to climate change.[1]. Meanwhile, an attribution study for floods in central Europe in July 2021 showed that climate change had increased the intensity of maximum daily rainfall by between 3% and 19%.[2].

Flooded Brisbane River at Colleges Crossing, Ipswich, Queensland, Australia, 1 March 2022

Heat

The recent IPCC Working Group II report[3] highlighted some of the impacts we are already seeing from extreme heat in terms of biodiversity and heat stress, for example in cities, in many regions of the world.

July 2019 saw record temperatures in the UK and Western Europe. In Cambridge, 38.7°C became the highest daily maximum temperature in the UK. An attribution study considered whether the intensity and probability of seeing such high temperatures in Europe have been influenced by climate change, concluding that the event was 10 times more likely in the UK and temperatures were 1.5 to 3° Higher C’s due to human-driven weather. change[4].

forest fires

In 2020, a rapid response review of 57 peer-reviewed articles[5] concluded that wildfires are becoming more severe and widespread, highlighting the links between climate change and increased frequency or severity of fire weather. This conclusion was supported in the IPCC Working Group I report[6] published in 2021 that stated that “fire weather conditions (composite events of heat, drought, and wind) have become more likely in some regions.”

In a high-risk region, studies under the Climate Science for Services Partnership (CSSP) Brazil project (supported by the UK government’s Newton Fund) have been looking at how wildfires in the Amazon rainforest may change in the future. future. Some of this work has led to the development of a fire probability forecasting service to help support planning strategies to reduce fire risk and impact.

droughts

The Iberian Peninsula is currently experiencing a prolonged winter drought that began in November 2021[7]. Identifying a direct link between climate change and drought is tricky, but there is growing evidence that our changing climate is influencing rainfall patterns in many regions of the world. The IPCC Working Group I report highlighted the increased prevalence of droughts observed in recent years.

Specific investigations have reached similar conclusions. Research within the CSSP China project indicated an increase in flash droughts. An attribution study focused on a severe drought that occurred between May and June 2019, in southwestern China, which severely damaged crops. At the peak of the event, the average rainfall was the lowest recorded since 1960 for the region and the lack of rain affected the drinking water supply of more than 824,000 people. Project scientists found that human-driven climate change increased the probability of such an event by a factor of six.[8].

A push for action

We can be more confident than ever in linking extreme weather events to climate change, as seen from the evidence above. The increasing chances of these extreme events continue to increase as long as we continue to emit greenhouse gases. The science is clear that the faster we reduce our greenhouse gas emissions, the more we can avoid the most severe impacts of climate change. Additionally, we must consider how we adapt to our changing climate to minimize the impacts we are already experiencing and can expect in the years to come. Later this month, we’ll take a look at what climate projections tell us about extreme events in the future.

Learn more about why we need to adapt to our changing climate here, and look for more on emission reductions (mitigation) next month.


[1] Davies et al 2021 https://rmets.onlinelibrary.wiley.com/doi/10.1002/wea.3955

[2] Kreienkamp et al 2021 https://biblio.ugent.be/publication/8732135/file/8732138

[3] IPCC, 2022: Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press. In press.

[4] World Weather Attribution https://www.worldweatherattribution.org/human-contribution-to-the-record-breaking-july-2019-heat-wave-in-western-europe/

[5] https://sciencebrief.org/briefs/wildfires

[6] IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press. In press.

[7] https://earthobservatory.nasa.gov/images/149469/iberian-peninsula-drought

[8] Lu et al. 2021 https://journals.ametsoc.org/view/journals/bams/102/1/BAMS-D-20-0128.1.xml

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