1. CO2 levels The amount of CO2 in the atmosphere reached record levels in 2020, hitting 417 parts per million in May. The last time CO2 levels exceeded 400 parts per million was around four million years ago, during the Pliocene era, when global temperatures were 2-4C warmer and sea levels were 10-25 metres (33-82 feet) higher than they are now.
2. Record heat The past decade was the hottest on record. The year 2020 was more than 1.2C hotter than the average year in the 19th Century. In Europe it was the hottest year ever, while globally 2020 tied with 2016 as the warmest.
3. Arctic ice Nowhere is that increase in heat more keenly felt than in the Arctic. In June 2020, the temperature reached 38C in eastern Siberia, the hottest ever recorded within the Arctic Circle. The heatwave accelerated the melting of sea ice in the East Siberian and Laptev seas and delayed the usual Arctic freeze by almost two months.
4. Permafrost Across the northern hemisphere, permafrost – the ground that remains frozen year-round for two or more years – is warming rapidly. When air temperatures reached 38C (100F) in Siberia in the summer of 2020, land temperatures in several parts of the Arctic Circle hit a record 45C (113F), accelerating the thawing of permafrost in the region. Both continuous permafrost (long, uninterrupted stretches of permafrost) and discontinuous (a more fragmented kind) are in decline.
5. Forests Since 1990 the world has lost 178 million hectares of forest (690,000 square miles) – an area the size of Libya. Over the past three decades, the rate of deforestation has slowed but experts say it isn’t fast enough, given the vital role forests play in curbing global warming. In 2015-20 the annual deforestation rate was 10 million hectares (39,000 square miles, or about the size of Iceland), compared to 12 million hectares (46,000 square miles) in the previous five years. >>>