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What would 4°C of global warming feel like?

COP26 is underway and keeping 1.5°C within reach will feature prominently in world leaders’ discussions.

The world is currently not on track to limit global warming to 1.5°C, and the targets announced in Paris would result in warming well above 3°C by 2100 compared to pre-industrial levels.

Limiting the average global temperature increase to 1.5°C could help avoid some of the most harmful impacts of climate change – including catastrophic flooding, bush fires, extreme weather, and destruction of species.

But what happens if we can’t meet the target? What if we warm the planet above 3°C?

Professor Robert Wilby, an expert in hydroclimatic modelling in the School of Social Sciences and Humanities, discusses what 4°C of global warming may feel like in The Conversation.

“Well for a start, whether the world warms by 1.5°C or 4°C, it won’t translate into the same amount of warming for everyone”, says Professor Wilby.

“Previous research with climate models has shown that the Arctic, central Brazil, the Mediterranean basin, and the mainland US could warm by much more than the global average.

“So, what might that mean for you in the years and decades to come? Statistics for ‘global mean temperatures’ and ‘regional hotspots’ are abstract concepts – helpful for policymakers, but not something anyone can actually feel. What’s more, temperature projections from global climate models are typically for wild or agricultural landscapes, averaged over tens to hundreds of square kilometres.

“These projections are far removed from the conditions that will be encountered on city streets, inside workplaces, public spaces, and our homes. But these are the places where health, comfort and productivity will be decided during the more intense heatwaves that climate change will bring.”

He continued: “One way of bridging the gap between climate models and the real world is to draw on personal memories of past extreme heat. Stop to think about the highest temperatures you’ve ever experienced outdoors in the shade.

“How about the hottest you’ve ever felt indoors? If I ignore saunas, mine was inside a home in Accra, Ghana. The room had wooden walls, a metal roof, and no air conditioning. Here, the temperature reached 38°C. Even though this was lower than in Melbourne, with the poor ventilation and humid air, the heat felt stifling.

“The highest outdoor temperature ever measured in the UK was 38.7°C on July 25 2019 in the Cambridge University Botanic Garden. According to UK Met Office analyses, global temperatures that are 4°C above pre-industrial levels may be reached as soon as the 2060s. Climate projections at the postcode level suggest that 4°C of global warming could bring temperatures of 43°C to Cambridge. I can now recall what a suburb felt like in Australia, and understand that this could be Cambridge in 40 years’ time.

“But this projection for the hottest summer day for Cambridge in the 2060s involved tuning climate models with temperatures averaged from weather stations. These tend to be located away from artificial heat sources and often in areas with grass and vegetation. Asphalt surfaces and high-density city centres are typically several degrees warmer and behave very differently to rural weather stations.”

“So, what might that room in Accra feel like with 4°C of global warming?”, asks Professor Wilby, “Indoor conditions will track outdoor temperatures because the room has no air conditioning. Worldwide, more than one billion people live in similar conditions. Without any adaptations, high indoor temperatures with high humidity could become unbearable – even deadly – for millions.

“Without action, the number of unbearably hot homes is set to grow. By 2050, 68% of humanity may live in urban areas and populations in the tropics will be most exposed to extreme humid heat. We know surprisingly little about these front lines of climate change, especially within the streets and homes of low-income communities.

“I will not forget that room in Accra, especially during the climate negotiations in Glasgow.”

Professor Wilby's quotes are taken from his Conversation article titled ‘Climate change: what would 4°C of global warming feel like?’. You can read the full article here.

Professor Wilby also authored a Conversation piece titled ‘London to be as hot as Barcelona by 2050? I research urban heat, and I’m sceptical’, which can be found here.

More content from Loughborough University’s PR team’s COP26 campaign can be found here

COP26 logo for the LU PR campaign

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