The current state of the climate

It cannot be denied that human influence has warmed the atmosphere, ocean and topography. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred. 

The scale of recent changes across the climate system as a whole and the present state of many aspects of the climate system are unprecedented over many centuries and millennia.

In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years, and concentrations of CH4 and N2O were at their highest level in at least 800,000 years.

Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years. Temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warming period, around 6,500 years ago.

The global nature of a glacier retreat, with almost all of the world's glaciers retreating synchronously since the 1950s is unprecedented in at least the last 2,000 years.

The average global sea level has risen faster since 1900 than over any preceding century in at least the last 3,000 years. The global ocean has warmed faster over the past century than since the end of the last deglacial transition.

Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heat waves, heavy precipitation, droughts, and tropical cyclones, and in particular, their attribution to human influence has strengthened.

Hot extremes have become more frequent and more intense across most land regions since the 1950s, while cold extremes have become less frequent and less severe. There is high confidence that human-induced climate change is the main driver of these changes.