Code Red for Humanity

The first part of the Sixth Assessment Report from the Intergovernment Panel on Climate Change finds that

It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.

Human activities are responsible for about 1.1 degrees Celsius of warming since the late 19th century and warming will likely exceed 1.5 degrees within 20 years.

But it is not just about temperature. Climate change is bringing multiple different changes in different regions – which will all increase with further warming. These include changes to wetness and dryness, to winds, snow and ice, coastal areas and oceans. For example:

Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.

Climate change is affecting rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon precipitation are expected, which will vary by region.

Coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion. Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.

Further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.

Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.

For cities, some aspects of climate change may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events and sea level rise in coastal cities.

Update (August 20):  Brian Tokar summarizes key points from the IPCC report. 

The report affirms much of what we already knew about the state of the global climate, but does so with considerably more clarity and precision than earlier reports. It removes several elements of uncertainty from the climate picture, including some that have wrongly served to reassure powerful interests and the wider public that things may not be as bad as we thought. The IPCC’s latest conclusions reinforce and significantly strengthen all the most urgent warnings that have emerged from the past 30 to 40 years of climate science.