The World Meteorological Organization (WMO) has revealed in its latest report that 2016 and 2019 were the hottest years in history, and the 2010s had the highest average temperature of any decade ever. And it says this trend will go on.

But let’s just wind back a bit.

In the last 650,000 years there have been seven great glacial periods, all interspersed with hot or interglacial periods in which the ice sheets retreated. These periods were provoked mostly by small changes in the amount of sunlight striking the earth, themselves caused by tiny changes in its orbit. Some briefer fluctuations in temperature have been prompted by periods of intense solar activity. Others were due to large amounts of very fine dust in the upper atmosphere, shot out of volcanoes as ash and suspended up there for years before causing a fall in the earth’s temperature. Historically, cyclical fluctuations between hot climates and extremely cold climates have always been incredibly gradual, over tens of thousands of years. So, none of the planet’s ecosystems have ever struggled to compensate for the very slow variations in temperatures. The last glacial period ended about 7,000 years ago, giving birth to the current climate cycle.

In the mid-19^th century, global warming took on a very different aspect. This time, according to NASA’s Goddard Institute, the event was very fast: a rise of 0.98 °C in under 40 years, between 1880 and 2019. So, it’s not just the average temperature of the earth and its oceans that is going up, but also the speed at which it does so. Almost every year sees new records set for monthly peaks in temperature, and every decade sees an increase of 0.3 °C. These data are accepted by the entire international scientific community and have been verified by drilling into permafrost and analysing growth rings in coral reefs or trees hundreds of years old, besides direct measuring.

So, what changed? In the last 100–150 years a new factor reared its head: the effect of human civilisation. Industrialisation, urbanisation, a growth in long-distance commerce, intensive farming and greater well-being in advanced countries demanded, and still demand, enormous quantities of energy. And producing it generates massive emissions of carbon dioxide, the same amount that accumulated in the subsoil in the hundreds of millions of years since the Palaeozoic Era. 

Throughout the earth’s history, decreases of 5–9 °C in temperature have caused Ice Ages and covered the continents of Europe and North America in ice sheets up to half a mile high. According to the Intergovernmental Panel on Climate Change (IPCC), the top international authority on climate change, the increase in average temperature that we’re now seeing is melting 3 mm of ice a year, including ice from the Arctic. In the hot July of 2019 alone, half a millimetre melted, which will push the waters up by 0.5–1 m by the end of the century. Though not easy to predict or quantify, the effect on various ecosystems will be far from negligible, with more frequent landslides, earthquakes and tsunamis, and huge quantities of carbon dioxide and methane released into the atmosphere (having been trapped until now in the ocean floor and permafrost). Plants and animals will move towards mountains and poles, as deserts expand over plains and over the equatorial and tropical zones. We will swing more quickly between periods of drought and intense rainfall, as heatwaves and cyclones become stronger and more regular.

Human societies are very much involved, not just as culprits but as victims. That goes for the poorest and the richest of them. In an article published in Nature in 2019, scientists from the Lancaster Environment Centre, a research institute in the city of the same name, quantified the damage done to the world economy by the melting of the ice caps at 70 trillion US dollars. To put that into perspective, the United States’ GNP in 2019 was 21 trillion dollars, the EU’s was 19 trillion and China’s 14 million. Rising water levels, shrinking arable land and disappearing fish and other animals will compromise infrastructure and settlements, and reduce the amount of food and drinking water available. It will be a short step from there to more social conflict and violence to get hold of whatever resources are left, plus big waves of migration.

If we’re to stop these things becoming a reality, we need strategies in place for lowering greenhouse gas production (especially carbon dioxide) and mitigating human impact on the ecosystem. But how? Well, by investing in renewable energies and new technologies, and cracking down on emissions. We’re looking at predictions with very different outcomes, as a study published on 22 April in Nature shows. The ongoing medical emergency of Covid-19 could be a new beginning, a chance for fresh cooperation between nations to avert the climate disaster. Or it could be a new end. We have alternatives, we just need to choose.