The climate crisis could cause up to 10,000 extra deaths in the UK every year by the 2050s as a result of extreme heat and bring a host of tropical diseases, a stark report has warned. The worst-case scenario, published in a damning document by the UK Health Security Agency (UKHSA) on Monday, would see average temperatures rise by 4.3C, bringing an estimated twelvefold rise in heat-related deaths by 2070. It adds that deaths could increase by one-and-a-half times in the 2030s. The figures come from UKHSA’s Health Effects of Climate Change (HECC) report, which examines the effects the climate crisis is already having on British health outcomes. It states that diseases transmitted by insects – such as dengue fever or Zika virus – could also become widely transmissible across the UK due to the arrival of species native to hotter countries. For example, the report suggests that the Asian tiger mosquito – which can transmit dengue, Zika and the chikungunya virus – has the potential to become established in most of England by the 2040s and 2050s, with most of Wales, Northern Ireland and parts of the Scottish Lowlands also becoming suitable habitats later on in the century. London could experience endemic dengue transmission by 2060, it adds. Prof Isabel Oliver, the chief scientific officer at UKHSA, said: “This report starkly demonstrates the impact that climate change could have on our society if we do not take decisive action. We can expect major impacts on physical and mental health, while our changing climate will also exacerbate existing health inequalities.” But UKHSA makes clear that many of these predictions stem from a worst-case scenario, and many of the adverse effects climate change has on health outcomes could be allayed. This could be accomplished through changed behaviour and mitigation. Such efforts include the use of national heat and cold alert systems and improvements to housing, specifically the use of energy efficient measures and flood defences. “In the UK many of the anticipated adverse impacts on health are still avoidable through mitigation measures, while others are preventable if the necessary adaptation measures are introduced. Therefore it is critical that the evidence in this report is used to inform policy and action,” Prof Oliver said. The report also outlines measures needed to be undertaken to mitigate the forthcoming damage – which includes the use of solar energy, energy-efficient lighting and passive or low-carbon heating and cooling. It says: “Extreme heat will lead to an increase in the number of deaths and other health effects due to warming temperatures and an ageing population. Up to 10,000 deaths a year due to extreme heat by the 2050s under a high-warming scenario without adaptation have been estimated.” The current worldwide goal of limiting global warming to below 1.5C has widely been accepted to be exceeded within the next five to 10 years, with the world currently on track to experience 2.7C of heating. Under UKHSA’s worst-case high-emissions scenario, cold-related deaths are also expected to increase for a brief period due to an ageing and growing population. It will then decline by the middle of the century, the report adds, with deaths from moderate cold peaking concurrently before seeing a decline by the 2070s. In 2022, more than 4,500 people died in England due to high temperatures – the largest figure on record. More than 2,800 excess deaths occurred among people aged 65 and over in England during that year’s heatwave. The 19 and 20 July of that year, when temperatures rose above 40C for the first time ever on record, saw a sudden spike in deaths, of 638 and 496 respectively. The report also makes clear that the worst health effects of climate change will disproportionately affect communities which are already vulnerable and disadvantaged, which could widen health inequalities even further. It says: “An ageing UK population will be an important driver of national climate vulnerability in relation to health over the coming decades. Climate risks to health will map on to existing gradients in health and inequality. “Those less able to control their environment, adapt their behaviours, or respond to new risks will be particularly vulnerable, including children, people with disabilities, people experiencing homelessness, and people in certain settings such as prisons, schools and social care.” Dr Lea Berrang Ford, the head of the Centre for Climate and Health Security at UKHSA, said the distribution of the impact will not be equal across individuals and communities. She added: “In the case of vector-borne disease, many of the risks will emerge first in the south of the country as we see the introduction of vector-borne disease risks coming up through Europe. “We see very similar patterns with climate change exacerbating existing health vulnerabilities, so these are communities or individuals who aren’t able to afford or access cooling technologies, cooling centres and different adaptation opportunities. The distribution of impacts in terms of climate change is unequal across a range of areas not only geographic but community level and individual.” The report also warns that under a high-emissions scenario, more people across the UK will be at risk of severe flooding, and that the greatest health impact this will have will be in regards to declining mental health. People who experience flooding are at higher risk of depression, anxiety and post-traumatic stress disorder. A government spokesperson said: “The UK is leading the way in tackling climate change – cutting emissions far faster than any other major economy and currently only accounting for 1% of global emissions. “The programme includes actions to develop climate-resilient health systems, working with the health and social care system to further improve the response to climate change, including extreme weather events.”