Climate change is already having an impact across the world in areas ranging from human health to agriculture and wildlife, a major international report has found.
Rising temperatures will increasingly threaten security, health and food supplies, and exacerbate poverty and damage species and habitats, the report from the Intergovernmental Panel on Climate Change (IPCC) warned.
The world is in "an era of man-made climate change" and has already seen impacts of global warming on every continent and across the oceans.
And experts warned that in many cases, people are ill prepared to cope with the risks of a changing climate.
The world has seen changes in recent decades to water resources as a result of melting glaciers and differences in rainfall, and reductions in wheat and maize yields.
There has been a decrease in the number of people dying from the cold but an increase in heat-related deaths in some areas, such as England and Wales, the report suggested.
Species including fish stocks are shifting their ranges, coral reefs are being damaged and wildfires are becoming more frequent.
The report on the impacts of climate change said rising temperatures are expected to lead to increased risk of flooding, more droughts and heatwaves, drive species extinct and cause forests to die in many regions of the world.
Food security will be hit by reduced yields in the major crops of wheat, rice and maize, while climate change will also exacerbate existing health problems, and lead to more heat wave-related deaths, malnutrition and disease.
Increasing numbers of people are set to be displaced by extreme weather events, and the impacts of rising temperatures could help increase the risk of violent conflicts by worsening problems such as poverty, the report said.
Recent extremes such as heat waves, droughts, floods and wildfires show how vulnerable humans are to variations in climate, the study warned.
While the impacts of climate change can be limited by action to reduce greenhouse gas emissions and by adapting to the changes, in many cases the world is ill-prepared to cope with the effects of rising temperatures.
And the greater the rise in temperatures, the more likely the world is to see severe and widespread impacts, or even reach "tipping points" which trigger abrupt and irreversible changes to the planet.
In the wake of the report's publication there were renewed calls from scientists and campaigners for action to cut greenhouse gases and to help vulnerable people adapt to already-unavoidable impacts of climate change.
Vicente Barros, co-chair of the IPCC study on climate change impacts, vulnerabilities and adaptation, from the University of Buenos Aires, Argentina said: "We live in an era of man-made climate change.
"In many cases, we are not prepared for the climate-related risks that we already face. Investments in better preparation can pay dividends both for the present and for the future."
In Europe, there will be increased economic losses and more people affected by flooding in river basins and coasts, in the face of rising sea levels and heavy rainstorms.
Most of the flood damage can be avoided by measures such as flood defences, but the costs of increasing protection will be high.
There will also be a reduction in water availability from rivers and groundwater, while increased heatwaves will damage human health and well-being, crop production and increase air pollution and the risk of wildfires in southern Europe and parts of Russia.
Professor Corinne Le Quéré, director of the Tyndall Centre for Climate Change Research at University of East Anglia said: "The human influence on climate change is clear.
"The atmosphere and oceans are warming, the snow cover is shrinking, the Arctic sea ice is melting, sea levels are rising, the oceans are acidifying, some extreme weather events are on the rise, ecosystems and natural habitats will be upset.
"Climate change threatens food security and world economies.
"We need rapid and substantial cuts in carbon emissions and a move away from burning fossil fuels if we are to limit global climate change below two degrees and mitigate these impacts."
Professor Sam Fankhauser, of the London School of Economics and a contributing author to the report said: "In the UK and the rest of northern Europe, we will need to cope with increasing risks from coastal and inland flooding, heat waves and droughts.
"The UK and all rich countries must also provide significant support to help poor countries, which are particularly vulnerable, to cope with the impacts of climate change."
The report from the IPCC forms the second part of a wide-ranging review of the evidence surrounding climate change.
The first part of the "fifth assessment report" which looked at the science of climate change, concluding there was a 95% chance that humans were responsible for the majority of global warming, was published last year.
The second part of the study drew on contributions from hundreds of experts from 70 countries, and more than 1,700 expert and government reviewers.