Before the 1980s, scientists were unsure whether pollution would warm or cool Earth
Until the 1980s it was genuinely unclear whether extra greenhouse gases would outweigh the cooling from airborne soot and particles. The answer is now plain. The air holds roughly half as much carbon dioxide again as before industrialisation, and 2024 was the warmest year since tracking began in 1850.
The mechanism is straightforward. Sunlight warms the Earth, which radiates heat back; greenhouse gases absorb part of that outgoing heat and warm the lower atmosphere. Burning coal, oil and gas since the Industrial Revolution, along with deforestation and some farming and industrial practices, has added these gases. Carbon dioxide, the main driver, has now reached levels unseen for millions of years. In 2024 the global average stood 1.60 degrees Celsius above the level at the start of regular records.
The language shifted along the way. Before the 1980s researchers spoke of inadvertent climate modification. Global warming, used as early as 1975, took off after NASA scientist James Hansen testified to the US Senate in 1988. Strictly, global warming means only the rise in average surface temperature, while climate change covers that plus knock-on effects such as altered rainfall; in a broad sense it also includes natural shifts across Earth's history.
Those effects are already visible. Heat waves and wildfires are more frequent, the Arctic is warming faster than elsewhere, thawing permafrost and shrinking glaciers and sea ice, and storms and droughts are intensifying. Species in mountains, reefs and the Arctic must move or die out. Ocean heating, acidification and sea level rise will continue for centuries whatever happens next. The World Health Organization ranks climate change among the largest threats to global health this century, and poorer communities, which emit least, are the most exposed.
For perspective, around 125,000 years ago the Last Interglacial ran 0.5 to 1.5 degrees warmer than pre-industrial times, with seas 5 to 10 metres higher, while 20,000 years ago the ice age was some 5 to 7 degrees colder and seas over 125 metres lower. The 2015 Paris Agreement aims to hold warming well under 2 degrees, but current pledges point to about 2.8 by 2100. Options include ending fossil fuel subsidies, saving energy, and shifting to wind, solar, hydro and nuclear power.
Source: Climate change
