Global temperatures have already increased by approximately 1°C since the beginning of the industrial age. Levels of carbon dioxide in the atmosphere are now higher than they have been for at least one million years.

Carbon dioxide (along with certain other greenhouse gases, or GHG) absorbs heat from the sun and reflects it back to earth, thus creating the “greenhouse” effect of warming the earth’s surface. Climate scientists have enumerated in great detail the effects this has already had on global ecosystems upon which we all depend for our survival.

We cannot predict exactly what will happen if the earth continues to heat up. We do know, however, that if all 25 billion tons of ice that sit on top of Antarctica were to melt, sea levels would rise by more than 200 feet. We also know that increased temperatures cause increased drought, so if temperatures continue to rise, this will eventually lead to catastrophic crop failure across all major grain-producing areas of the globe.

Other possible effects of uncontrolled climate change include the collapse of ecosystems and the mass extinction of species, mass migration of people as coastal areas flood and extreme temperatures make areas of the world uninhabitable, and extreme weather events causing even more migration and disruption, as well as physical damage costing trillions of dollars to the global economy.

The Paris Climate Agreement, reached in December 2015, committed every country in the world to do what they could to prevent global warming from reaching 2°C above pre-industrial levels. Many campaigners at the time felt that a limit of 2°C was too high to prevent runaway climate change.

In November 2018, the latest report from the Inter-governmental Panel on Climate Change (IPCC) confirmed their worst fears. The verdict from the world’s leading climate scientists is that allowing global temperatures to increase to 2°C above pre-industrial levels will create instabilities and extremes in global weather patterns which could be catastrophic to human civilisation as we know it.

Avoiding the most extreme effects of climate change will require, according to the IPCC report, a 45% cut in global carbon emissions by 2030, reaching a target of net-zero carbon emissions by 2050. This is required to keep global warming to no more than 1.5°C above pre-industrial levels.

Even 1.5°C of global warming will have serious consequences. Going beyond that is now too dangerous to contemplate.

Why is a Green New Deal the only real solution to the climate crisis?