People may have to be moved away from high-risk areas as climate change makes flooding more likely and more severe in the UK, the government has said.

The warning came as a Met Office report found Britain would experience much wetter winters and summers as much as 5C hotter as a result of climate change. This year’s heatwave is likely to become the new normal by mid-century, but the wettest days are now on average seeing 17% more rainfall than in the recent past, bringing a much heightened risk of flash flooding.

Announcing the biggest review of climate change in Britain for nearly a decade, the environment secretary, Michael Gove,said flooding was one of the key ways in which changes would become manifest in the UK.

Quick Guide UK climate projections 2018 – key findings Show • Summers in the UK for the last decade have been on average 20% wetter than the 1961-1990 average

• Total rainfall from extremely wet days has increased by about 17% in the last decade, showing that extreme weather – which can lead to flash flooding – is growing more common • The mean sea level around the UK has risen by about 16% since the start of the 20th century, and sea level rises could reach 1.15m by 2100 • By 2070, summers could be 5.4C hotter, and winters 4.2C warmer • The chance of a summer as hot as 2018 was only about 5% in the 1990s but is now a 10-20% probability, rising to a 50% probability by mid-century • The average temperature in the UK for the past decade has been 0.3C warmer than the 1981-2010 average, and 0.8C warmer than the 1961-1990 average • Nine of the 10 warmest years on record in the UK have occurred since 2002 • The average hottest day of the year in the last decade has been on average 0.1C hotter than the 1981-2010 average, and 0.8C warmer than the 1961-1990 average of 26C • Sea level rise is likely to be greater in the south than the north, with London expected to be in the range of 0.29-0.7m by the end of the century if greenhouse gas emissions are kept low, but 0.53-1.15m if emissions are high. Edinburgh is likely to experience a rise of only 0.08-0.49m in a low-emissions scenario, and 0.3-0.9m if emissions are high The projections are available online through the Met Office, and next year a more detailed assessment will be issued showing the risks of climate change at a more local level, comparable to those used for weather forecasting and providing information on events such as localised heavy rainfall, which can result in flash floods and surface water floods

“It will not always be possible to prevent every flood,” he told an audience of Department for Environment, Food and Rural Affairs (Defra) stakeholders. “We cannot build defences to protect every single building or reinforce every retreating coastline. We will be looking at ways we can encourage every local area to strive for greater overall resilience that takes into account all the different levers from land-use planning to better water storage upstream, and tackles both flood prevention and response.”

Defra is spending £2.6bn on flood defences between 2015 and 2021, and aims to protect 300,000 homes from flooding by that date. The Met Office said the UK could expect warmer and wetter winters as a result of climate change.

The Environment Agency is preparing for 4C of warming in planning the UK’s flood defences, though the Paris agreement aims to limit warming to no more than 2C above pre-industrial levels. Even in the lowest-emission scenario presented by the report, average annual temperatures are expected to be up to 2.3C higher by the end of the century.

The chance of seeing a summer as hot as 2018 was less than 5% in the 1990s, but already that risk is between 10% and 20%, and by mid-century will be 50%, according to the projections. But while summers grow hotter, they will also be wetter in some places, with the average summer now 20% wetter than the average between 1961 and 1990.

Gove said: “We need our communities and infrastructure to be better prepared for floods and coastal change, so that they recover more quickly from the damage and disruption and, where necessary, to help people and communities move out of harm’s way.”

New flood protection measures will include natural defences such as planting trees, restoring heathland and installing “leaky dams”, as well as in some cases allowing water to breach sea walls to create new wetland habitats for birds.

Next year, Defra will publish a long-term policy statement on flooding and coastal erosion and the Environment Agency will issue a new 50-year flood strategy, which Gove said should “explore new philosophies”, going beyond traditional flood defences such as sea and river walls and other “hard” barriers.

Quick Guide New environment policies Show Flooding Defra is to publish a long-term policy statement on flooding next year, while the Environment Agency will issue a new 50-year strategy at the same time. These are likely to include measures far beyond traditional flood management, which relies on “hard” defences such as seawalls and river barriers, and focus on soft defences such as restoring wetlands, planting trees, providing more natural spaces for water storage and moving people away from the worst affected areas. Water supply This week, Defra will publish a new draft national policy statement containing measures to make it easier for water companies to construct new reservoirs and water infrastructure. There will also be a new target for water companies to halve leakage from their pipes by 2050. Agriculture The agriculture bill currently before parliament will reward farmers who reduce greenhouse gas emissions and help to adapt their land to a changing climate. Next year, Defra will start developing a new emissions reduction plan for agriculture, including ways to reform fertiliser use, which produces greenhouse gas emissions and ammonia, a key contributor to air pollution. Nature A new England Peat Strategy will be published next year setting out how to restore peatlands. A new task force is to be set up to accompany the strategy. A new English Tree Strategy will set out how to accelerate tree planting. From 2024, farmers will be rewarded for woodland creation through the environmental land management contracts set out in the agriculture bill. Waste and resources Defra will develop a new resources and waste strategy, setting out measures to improve the use of resources, increasing re-use and recycling, minimising waste and creating a more circular economy. Food waste will be a priority, with more councils encouraged to collect food waste separately and send it to anaerobic digestion plants to create biogas for domestic heating. A new £15 fund will redistribute surplus food to charities. International The UK will ensure its international aid supports work dealing with climate change and biodiversity loss, and share expertise with developing countries to help them adapt to the effects of warming. A new £13m fund will target mangrove restoration, particularly in small island states such as Jamaica, and countries hit by deforestation, such as Colombia. The UK will also participate in the new Global Commission on Adaptation, chaired by Ban Ki-moon, and will push for a new international agreement on biodiversity at a key conference in China in 2020.

Gove said the new data in the UK Climate Projections report, compiled by Defra and the Met Office, would help communities and businesses to protect themselves better from the increasing flood risk.

In a wide-ranging speech, the secretary of state also promised new domestic policies aimed at reducing greenhouse gas emissions, using resources more efficiently and tackling waste, planting more trees and restoring peatlands.

Next year an England Peat Strategy will be published, setting out how the condition of the country’s peatlands – only 13% of which are in near natural condition – will be improved. A new taskforce will also be set up, involving farmers, conservationists and academics.

Farmers will be central to many parts of the climate strategy, with Gove promising reforms around how fertilisers are used and a new emissions reduction plan for agriculture, at the same time as encouraging farmers to grow more food. Farmers would be supported by the government in reducing the emissions from their land and activities, Gove said, but he did not specify what form this support would take.

New water supply infrastructure will also be needed, and Gove raised the possibility of new reservoirs, which could prove controversial in some areas. This week, the government will lay before parliament a new draft national policy statement that will set out measures to make it easier for water companies to build reservoirs and water transfer infrastructure.

Water companies have set out proposals for more than £50bn of investment between 2020 and 2025, which are now under scrutiny by Ofwat to ensure they represent value for money for the public.

Gove made it clear that his ambitions for tackling climate change were also international. “We are a world leader in supporting international development, both financially and through technical assistance,” he said, noting that the UK was the world’s third-largest aid donor.

“Climate change and other interrelated environmental impacts are exacerbating poverty and erasing, or increasing the fragility of, development gains, and the crisis facing our natural world is growing,” he said. “Protecting and restoring nature is essential for securing genuinely sustainable development. That is why we need to ensure that our funding for international development supports work to deal with climate change and biodiversity loss.”

He pointed to £6bn of funding earmarked for the period 2016 to 2020 to help developing countries curb their greenhouse gas emissions and build resilience to the impacts of climate change. “Between now and 2020 it is also critical that we better connect the international climate negotiations with those focused on nature and biodiversity,” he said. “It is impossible to meet climate mitigation and climate adaptation objectives without the natural environment, and we can’t save nature without tackling climate change.”

UN talks on how to implement the Paris agreement will take place next month in Poland but progress may be made difficult by the withdrawal of the US and the anti-Paris stance taken by Brazil’s new president, Jair Bolsonaro.

Campaigners urged the government to do more. Emi Murphy of Friends of the Earth said: “Climate change will have a devastating impact on the UK with more extreme weather, rising sea levels and scorching summers – so why isn’t the government doing far more to tackle this crisis? Ministers must develop an urgent action plan to develop a zero-carbon future – and strengthen the Climate Change Act to ensure this is achieved.”