courtesy  :  wikipedia

Climate change

Contemporary climate change includes both global warming and its impacts on Earth’s weather patterns. There have been previous periods of climate change, but the current changes are distinctly rapid and are not due to natural causes.^[2] Instead, they are caused by the emission of greenhouse gases, mostly carbon dioxide (CO₂) and methane. Burning fossil fuels for energy use creates most of these emissions. Agriculture, steelmaking, cement production, and forest loss are additional sources.^[3] Greenhouse gases are transparent to sunlight, allowing it through to heat the Earth’s surface. When the Earth emits that heat as infrared radiation the gases absorb it, trapping the heat near the Earth’s surface. As the planet heats up it causes changes like the loss of sunlight-reflecting snow cover, amplifying global warming.^[4]

On land, temperatures have risen about twice as fast as the global average. Deserts are expanding, while heat waves and wildfires are becoming more common.^[5] Increased warming in the Arctic has contributed to melting permafrost, glacial retreat and sea ice loss.^[6] Higher temperatures are also causing more intense storms and other weather extremes.^[7] In places such as coral reefs, mountains, and the Arctic, many species are forced to relocate or become extinct, as their environment changes.^[8] Climate change threatens people with food and water scarcity, increased flooding, extreme heat, more disease, and economic loss. It can also drive human migration.^[9] The World Health Organization calls climate change the greatest threat to global health in the 21st century.^[10] Even if efforts to minimise future warming are successful, some effects will continue for centuries. These include sea level rise, and warmer, more acidic oceans.^[11]

Many of these impacts are already felt at the current level of warming, which is about 1.2 °C (2 °F). The Intergovernmental Panel on Climate Change (IPCC) projects even greater impacts as warming continues to 1.5 °C and beyond.^[12] Additional warming also increases the risk of triggering tipping points, such as the melting of the Greenland ice sheet.^[13] Responding to these changes involves taking actions to limit the amount of warming, and adapting to them.^[14] Future warming can be reduced (mitigated) by lowering greenhouse gas emissions and removing them from the atmosphere.^[14] This will involve using more wind and solar energy, phasing out coal, and increasing energy efficiency.^[15] Switching to electric vehicles, and to heat pumps for homes and commercial buildings, will further limit emissions.^[16] Prevention of deforestation and enhancing forests can help absorb CO₂.^[17] Communities may adapt to climate change through better coastline protection, disaster management, and development of more resistant crops. By themselves, these efforts to adapt cannot avert the risk of severe, widespread and permanent impacts.^[18]

Some effects of climate change, clockwise from top left: Wildfire intensified by heat and drought, bleaching of coral caused by ocean acidification and heating, and worsening droughts compromising water supplies.

Under the 2015 Paris Agreement, nations collectively agreed to keep warming “well under 2 °C” through mitigation efforts. However, with pledges made under the Agreement, global warming would still reach about 2.7 °C by the end of the century.^[19] Limiting warming to 1.5 °C would require halving emissions by 2030 and achieving net-zero emissions by 2050.^[20]

Before the 1980s, it was unclear whether warming by increased greenhouse gases would dominate aerosol-induced cooling. Scientists then often used the term inadvertent climate modification to refer to the human impact on the climate. In the 1980s, the terms global warming and climate change were popularised. The former refers only to increased surface warming, the latter describes the full effect of greenhouse gases on the climate.^[22] Global warming became the most popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate.^[23] In the 2000s, the term climate change increased in popularity.^[24] Global warming usually refers to human-induced warming of the Earth system, whereas climate change can refer to natural or anthropogenic change.^[25] The two terms are often used interchangeably.^[26]

Various scientists, politicians and media figures have adopted the terms climate crisis or climate emergency to talk about climate change, and global heating instead of global warming.^[27] The policy editor-in-chief of The Guardian said they included this language in their editorial guidelines “to ensure that we are being scientifically precise, while also communicating clearly with readers on this very important issue”.^[28] In 2019, Oxford Languages chose climate emergency as its word of the year, defining it as “a situation in which urgent action is required to reduce or halt climate change and avoid potentially irreversible environmental damage resulting from it”.^[29][30]