6 years after the Paris Agreement

Through the Paris Agreement in 2015, the international community agreed to keep global temperature rise this century well below 2.0°C degrees above pre-industrial levels, and to pursue efforts to limit temperature increase to 1.5°C. The 1.5°C threshold is important because beyond this, so-called “tipping points” – positive feedback loops where global warming causes a permanent shift in earth systems, locking in further warming – become more likely.

The IPCC climate change report brings forward when scientists expect to reach 1.5C to the mid-2030s, at which point tipping points such as lose of artic sea ice, larger-scale die-offs of coral reefs, and thawing of the methane-rich permafrost become much more likely.

Increased CO2 will have dire long-term effects

Another core concept in the IPCC report about climate change is the long-term effect of increased CO2 in the air. The Earth takes time to adjust to increases of CO2 in the air, and the Equilibrium Climate Sensitivity (ECS) estimates how much the earth will warm with a doubling of the amount of CO2 in the air. This is important because CO2 has increased from its pre-industrial level of around 280 parts per million (ppm) to an estimated 415 ppm today, with a predicted doubling of CO2 in the air around 2060.

Recent research predicts the increase in global average temperature with a doubling of CO2 in the air to between 2.6-4.5C. The difference between 1.5C short term, and between 2.6C and 4.5C longer term may seem small at first glance. However, the difference between 1.5C, 2C, and 3C is the difference between average droughts lasting two, four or 10 months per year, and the difference between 6%, 18% or 68% (for an increase to 4.5C) means invertebrates globally losing their habitat. These longer-term trends are in addition to the extreme weather we have witnessed across Europe and the US over the past two months.

> Read more about it: New climate change report shows need for urgent action – here’s how leaders can act