To avert potential and catastrophic effects on both humans and ecosystems, we must prevent global temperatures from rising by more than 2º Celsius above pre-industrial levels. (1)

The IPCC indicates that temperatures have increased approximately 1ºC in the last 100 years. (2) Therefore, we must not allow more than another degree rise in the average global temperature.

Devastating impacts

A 2ºC rise is the point at which some of the most devastating and dangerous processes brought on by climate change could become unavoidable. These include:

• The melting of the West Antarctic and Greenland ice sheets, which between them could raise global sea levels by up to 7 meters. (3)
• The drying of many parts of Africa,
• The inundation by salt water of the aquifers used by cities such as Shanghai, Manila, Jakarta, Bangkok, Kolkata, Mumbai, Karachi, Lagos, Buenos Aires and Lima.(4)
• The risk of water shortages for between 2.3 and 3 billion people. (5) The melting of glaciers will imperil people who depend on their meltwater, such as (6)
  • people from Pakistan, western China, south-east and central Asia (the Himalayas)
  • people in Peru, Ecuador and Bolivia (the Andes)
  • people in British Columbia and Canada’s prairie provinces (the Rockies)
• The bleaching of 95% of the world’s coral. This bleaching would result in the death of almost all of the world’s coral and the destruction of those ecosystems.(7)

Runaway, positive feedback

Above 2ºC, three key positive feedback mechanisms may pass the point of no return. These mechanisms will accelerate the warming without any involvement from us:

• the melting permafrost begins to release the methane it contains (8)
• the Amazon rainforest dies off, turning trees back into carbon dioxide (9)(10)
• the possible release of massive volumes of methane beneath the ocean bottom known as clathrates (11)

In other words, if the planet warms by 2º then 3º or 4º (or more drastic) change becomes almost inevitable.

To prevent this temperature increase, we must reduce our greenhouse gas emissions by 90% before 2030. (12)