Climate Change – The Latest Assessment of the Science, Impacts and Risks of Climate Change

The Earth’s climate has always been changing, but human activities are adding a lot of extra heat. This is called the greenhouse effect and it traps some of the sun’s heat, warming our planet. Some of the heat-trapping gases in the atmosphere are naturally occurring, but many have been added by humans. The largest one is carbon dioxide (CO2). The natural world has adapted to these changes over millions of years, but human-caused climate change is pushing some systems close to their limits.

Global temperatures are rising, and sea levels are rising faster than ever. Many ecosystems are shifting, and species are going extinct. Droughts are becoming more frequent and intense, threatening crops and freshwater supplies. Seas are getting warmer and more acidic. Oceans are losing ice sheets and glaciers, and their loss contributes to sea level rise. The Arctic is heating up twice as fast as the rest of the planet, and melting polar sea ice is contributing to sea level rise and causing more extreme weather events.

While some people think these changes are just part of natural processes, the overwhelming majority of scientists agree that they are mostly caused by human activity and that we are responsible for a significant portion of the current warming trend. The Intergovernmental Panel on Climate Change (IPCC) has set a target of limiting global temperature increases to below 2 degrees Celsius. Scientists believe that this limit is necessary to avoid crossing important “tipping points” – the point at which the speed of changes will accelerate and become irreversible, for example the collapse of the Greenland Ice Sheet.

The IPCC’s latest assessment of the science, impacts and risks of climate change provides a wealth of information to guide policy decisions. It presents a range of pathways for 21st century emissions, from stringent mitigation to high emission scenarios. These are defined by Representative Concentration Pathways (RCPs), which vary from RCP2.6, through to RCP8.5. The pathways show how much extra heat the planet will trap with each extra increase in emissions, and the impact of those additional emissions on different parts of the world.

There is very high confidence that the average temperature of Earth will continue to rise throughout this century. Warming will cause sea levels to rise, with more frequent and severe coastal flooding in low-lying areas and increased erosion. Arctic melting and thawing of permafrost will add to sea level rise. The ocean is also becoming more acidic, which will threaten marine life and alter marine ecosystems.

Climate change is already affecting the lives of many people, especially in low-income and vulnerable countries and communities. The climate crisis is harming health, putting food and water security at risk, and making it harder for many people to survive. The people most at risk are those who contributed the least to the causes of climate change and have the least ability to protect themselves. This includes indigenous communities and people living in rural areas, particularly women.

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