Extreme events on the increase in a changing climate

Earlier this month Professor Peter Stott examined extreme weather events around the world and how attribution studies can assess whether these are as a result of anthropogenic (human-induced) climate change. But what does the future hold? Can we expect to see more extreme events? Here we explore what the science tells us in relation to droughts, heat, wildfires and rainfall/flooding.

Rainfall/flooding

We mentioned in our earlier blog post that an attribution analysis of the wettest February on record for the UK (which occurred in 2020) showed that the extreme rainfall experienced could become nine times more likely by the end of the century than in pre-industrial times[1]. Wet weather events such as these are expected to increase over the coming decades in the UK.

The latest Intergovernmental Panel on Climate Change (IPCC) report states that “it is virtually certain that, in the long term, global precipitation will increase with increased global mean surface temperature”. Warmer air holds more moisture, which is one of the reasons a rise in global temperatures will result in more rainfall in some regions around the world. Particularly high levels of precipitation can occur due to slow-moving storms, with the potential for high rainfall accumulations projected to be fourteen times more frequent across Europe by 2100 (for 4.3°C of global warming – a high emissions scenario)[2].

Natural variability, particularly in places such as the UK, can make it more difficult than with temperature extremes to separate the contribution of anthropogenic climate change from other influences on heavy rainfall events. It is not yet possible to discern underlying changes in local rainfall extremes above natural variability using only the observation record[3]. Research following record-breaking rainfall in October 2020 has indicated, however, that days with extreme rainfall accumulations will become more frequent through the century[4].

Heat

In the UK and around the globe, recent years have seen a number of record-breaking temperatures. In June 2021 Canada hit its highest recorded temperature of 49.6°C – you can find out more about this in our latest MostlyClimate podcast with a guest speaker from Environment and Climate Change Canada – and Australia recorded its joint hottest day on record in January of this year with 50.7°C.

In the UK we can expect to see hotter, drier summers in the future, with temperatures similar to the 2018 joint-hottest summer on record around 50% more likely by 2050 even in a low emissions scenario[5]. A study following the highest recorded UK temperature (38.7°C in July 2019) considered whether exceeding 40°C is within the possibilities of the UK climate[6]. Lead author, Met Office Senior Scientist Dr Nikolaos Christidis, concluded that, “the likelihood of exceeding 40°C anywhere in the UK in a given year has been rapidly increasing, and, without curbing of greenhouse gas emissions, such extremes could be taking place every few years in the climate of 2100.”

If the average global temperature reaches 2°C above pre-industrial levels, the number of people in regions across the world affected by extreme heat stress – a potentially fatal combination of heat and humidity – could increase nearly 15-fold. The new interactive atlas from the Intergovernmental Panel on Climate Change (IPCC), which shows possible climate futures for temperature and precipitation, highlights the importance of minimising future global warming.

Wildfires

Wildfires are often tied with significant drought in the UK. Increased temperatures and reduced humidity[7] are likely to lead to a greater risk of fire danger in the UK by the end of the century if temperatures are not kept below 2°C and even at this level of warming the risk could double[8].

A recent United Nations Environment Programme report has predicted that even if greenhouse gases are reduced, there could be a global increase in extreme wildfires of up to 50% by the end of the century. The report, which included contributions from the Met Office and the UK Centre for Ecology & Hydrology, found that some of the biggest increases will be in areas not typically used to seeing wildfires, such as the Arctic and central Europe. Areas of tropical forest in Indonesia and the southern Amazon are also likely to see increased burning if greenhouse gas emissions continue at their current rate.

Research published on the Amazon rainforest last year found that a shift to hotter and drier conditions in the future could result in a greater burned area and resultant fire emissions. The Amazon rainforest is a natural carbon sink, removing and storing carbon from the atmosphere. With global warming limited to 1.5°C above pre-industrial levels, climate model experiments show a reduction in carbon storage of 7%. However, if warming were to increase to 4°C, the loss of carbon storage from these ecosystems could be as much as 30% highlighting the importance of understanding the link between climate change, fire risk and the carbon cycle which could be used to inform fire and land-use management strategies.

Droughts

2010-2012 saw an exceptional drought in the UK, one of the most significant for some regions of England in 100 years[9]. Research published last year using UKCP18 data indicated higher frequency and more severe long-term droughts in the UK, with droughts at least as severe as the one experienced in 2010 increasing by 86% at a 2.0°C level of global warming and by 146% at 4.0°C. The chart below also shows how summers are expected to become drier relative to typical conditions across both southern and northern Europe between now and 2100, with more extreme dry summers in the south[10].

A climate risk report completed earlier this year for the East Africa region indicates a projected increase in variability of seasonal rainfall could result in more frequent wetter and drier years and a higher risk of flood and drought events. These have the potential to impact socio-economic development by affecting sectors such as agriculture, electricity generation and health.

Taking action to minimise impacts

As explored earlier this month, we are already seeing an increase in extreme events attributable to climate change. Climate projections clearly indicate that we can expect further rises in many of these in the coming decades both in the UK and around the world. Limiting carbon emissions in order to minimise future warming can help stave off the worst of these impacts, which is why the 2021 Glasgow Climate Pact recognised the imperative to ‘keep 1.5°C alive’ and ensure that global temperatures do not go above this level. In order to combat the effects of these extreme events, we will also need to adapt to our changing climate, recognising that we are already seeing impacts and that, even if we stopped all carbon emissions today, we would see impacts of climate change long into the future.

We have been sharing information on extreme events on our social media channels this month. Follow #GetClimateReady to learn more and look out for a focus on mitigation soon.


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

[2] Kahraman et al 2021 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL092361

[3] Kendon et al 2018 https://journals.ametsoc.org/view/journals/clim/31/7/jcli-d-17-0435.1.xml

[4] Christidis et al. 2021 https://rmets.onlinelibrary.wiley.com/doi/10.1002/asl.1033

[5] UKCP18

[6] Christidis et al 2020 https://www.nature.com/articles/s41467-020-16834-0

[7] Arnell et al https://centaur.reading.ac.uk/96625/8/Arnell_2021_Environ._Res._Lett._16_044027.pdf

[8] Perry et al https://nhess.copernicus.org/articles/22/559/2022/nhess-22-559-2022-discussion.html

[9] Kendon et al https://rmets.onlinelibrary.wiley.com/doi/10.1002/wea.2101

[10] https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2021/drier-european-summers-projected-under-human-induced-climate-change

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