Climate change

• 1. Defining The Climate Crisis

  ›

  In 1988, NASA climate scientist James Hansen testified before the U.S. Senate and used the phrase global warming to describe human-caused temperature rises. Before that decade, scientists called this phenomenon inadvertent climate modification because they were unsure if greenhouse gases warmed the planet more than air pollution cooled it. Today, researchers distinguish between global warming as a specific rise in average surface temperatures and climate change as the broader set of effects including extreme weather and ocean acidification. The Intergovernmental Panel on Climate Change states that observed warming from 2014 to 2023 averaged 1.19 degrees Celsius above pre-industrial levels. This modern rise is driven by burning fossil fuels like coal, oil, and natural gas since the Industrial Revolution began. Atmospheric carbon dioxide concentrations have increased by roughly 50% compared to the end of the pre-industrial era. Methane and nitrous oxide levels are now higher than at any point in the last 800,000 years.

• 2. Historical Temperature Trends

  ›

  Instrumental records covering the period from 1880 to 2012 show multiple datasets confirming that recent decades have warmed unequivocally. Between the 18th century and 1970, there was little net warming because sulfur dioxide emissions created cooling aerosols that offset greenhouse gas heat. After 1970, controls on sulfur pollution allowed temperature to rise sharply alongside accumulating greenhouse gases. The 2014, 2023 decade reached an average of 1.19 degrees Celsius warmer than the 1850, 1900 baseline. From 1998 to 2013, a slowdown known as the global warming hiatus occurred due to Pacific Decadal Oscillation patterns. In 2024, temperatures exceeded the recent average by more than 1.5 degrees Celsius. Over the last few million years, Earth cycled through ice ages with periods like the Last Interglacial being 0.5 to 1.5 degrees warmer than today. Sea levels during that ancient warm period stood 5 to 10 meters higher than current measurements.

• 3. Greenhouse Gas Drivers

  ›

  Human activity since the Industrial Revolution has increased atmospheric carbon dioxide by about 50% and methane by roughly 164% compared to 1750 levels. Global human-caused greenhouse gas emissions in 2019 equaled 59 billion tonnes of carbon dioxide equivalent. Seventy-five percent of these emissions came from carbon dioxide generated by burning fossil fuels for transport, manufacturing, heating, and electricity. Methane emissions arise from livestock enteric fermentation, manure management, coal mining, landfills, oil extraction, wastewater treatment, and rice cultivation. Nitrous oxide largely results from microbial decomposition of fertilizers used in agriculture. Carbon dioxide remains in the atmosphere for centuries while methane lasts only an average of 12 years. Land-surface carbon sinks absorb about 29% of annual global emissions while oceans take up another 20 to 30%. The remaining fraction stays in the air until stored in the Earth's crust over millions of years.

• 4. Environmental Tipping Points

  ›

  The Greenland ice sheet is already melting but will continue disappearing if warming reaches between 1.7 and 2.3 degrees Celsius even if temperatures later drop. Melting ice sheets near the poles weaken ocean currents like the Atlantic meridional overturning circulation which distributes heat globally. Ocean acidification makes it harder for mussels, barnacles, and corals to build shells and skeletons due to increased dissolved carbon dioxide. Dead zones are expanding as oxygen becomes less soluble in warmer water. Over 90% of extra energy from global warming has been absorbed by the ocean since at least 1970. Sea levels rose at a rate of 4.8 centimeters per decade between 2014 and 2023. Under high emission scenarios, sea level rise could reach two meters by 2100 due to marine ice sheet instability in Antarctica. Deep oceans below 2,000 meters are committed to losing over 10% of their dissolved oxygen by current warming levels.

• 5. Human Health And Inequality

  ›

  The World Health Organization identifies climate change as one of the biggest threats to global health in the 21st century. Extreme weather events increase illness and death rates while affecting food and water security. Scientists project that 14.5 million more deaths will occur due to climate change by 2050. Thirty percent of the global population currently lives in areas where extreme heat and humidity cause excess deaths. By 2100, half to three-quarters of humanity may live in such conditions. Heat stress can reduce labor capacity by 30 to 50% in regions like South-East Asia if warming reaches 4 degrees Celsius. The World Bank estimates that climate change could drive over 120 million people into extreme poverty between 2016 and 2030 without adaptation measures. Indigenous communities face endangerment to wellness and lifestyles because they depend directly on land and ecosystems. Women often bear heavier work burdens during climate shocks due to discriminatory norms limiting their resources.

• 6. Global Mitigation Strategies

  ›

  Renewables represented 86% of all new electricity generation installed globally in 2023. To achieve carbon neutrality by 2050, renewable energy would need to become the dominant form of electricity generation rising to 85% or more in some scenarios. Investment in coal must be eliminated and coal use nearly phased out by mid-century. Electricity from renewables must also power heating systems and transport networks through electric vehicles and public transit. Battery storage can expand to match variable wind and solar outputs with long-distance transmission lines. Carbon dioxide removal techniques include reforestation, afforestation, and soil management practices like winter cover crops. Direct global fossil fuel subsidies reached $319 billion in 2017 while indirect costs totaled $5.2 trillion. Ending these subsidies could reduce global carbon emissions by 28% and air pollution deaths by 46%. The Paris Agreement aims to keep warming well under 2 degrees Celsius but current pledges suggest a 66% chance of reaching 2.8 degrees by century's end.