Human activities have had an “unequivocal” influence in warming the world’s atmosphere, oceans and land. This is the conclusion of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) released in August 2021. According to the report, global average surface temperatures were 1.1°C higher in the past decade than they were in the 1850 – 1900 time period – a rate of warming that is unprecedented in at least the last 2000 years.
The IPCC Report brings together the latest advances in climate science and has the most up-to-date understanding of the earth’s climate system. It observes that sea level rise is now faster than at any time in at least 3,000 years. Arctic sea ice has shrunk to its smallest area in at least 1,000 years and the rate at which glaciers are receding is unmatched in at least 2000 years.
The IPCC points to carbon dioxide emissions in the atmosphere as the largest contributor to climate warming. The concentration of CO2 in the atmosphere is the highest it has been in at least 2 million years.
When fuels like natural gas, oil and coal are burned to produce energy, CO₂ is the by-product. CO₂ in the atmosphere prevents earth’s heat from being radiated out into space, much like glass traps heat in a hothouse. The more fossil fuels are burned, the more CO₂ will end up in the atmosphere.
Climate warming has risks. The IPCC cites the increasing frequency and intensity of weather extremes such as heatwaves, heavy precipitation, flooding, droughts, and tropical cyclones. The report has high confidence that human-induced climate change is the driver of these observed trends.
Over the next twenty years, the global average temperature is expected to rise by over 1.5 °C if no action is taken soon. With every increment of global warming, changes in regional mean temperatures get larger (Graph 2).
To avoid the most undesired outcomes from a warming climate, the IPCC 6th Assessment Report calls for CO₂ emissions produced from human activities to reach net zero. According to the report, the world’s energy supply and end-use sectors will need to be decarbonized.
Technologies that improve energy efficiency, carbon capture, zero-emission vehicles and low carbon alternative refrigerants are only a few examples of potential solutions.
The IPCC was created in 1988 by the United Nations Environment Program and the World Meteorological Organization (WMO) to “provide governments at all levels with scientific information that they can use to develop climate policies”. The 6th Assessment was authored by 234 experts and scientists from 65 countries