A1F1

I am reading a book called Requiem for a Species¹ by Clive Hamilton. 

In Hamilton's terms: 

"This book is about why we have ignored those (Climate Change) warnings, so that now it is too late." 

In the 1990’s the IPCC² developed a number of scenarios to reflect future influences on emissions and associated warming. The worst-case scenario is known as A1F1.

In A1F1 IPCC anticipated growth in CO₂ emissions of 2.5% per annum through to 2030, yet we have seen that from around 2000 global emissions began growing at 3% a year.

The IPCC’s Fourth Assessment Report, published in 2007, narrowed the likely range of warming to 2.4 to 4.6°C above pre-industrial levels by 2100 if we do nothing.

The upper limit of 4.6°C became the most likely outcome for the A1F1 scenario since emissions grew faster than projected by IPCC in 1990’s.

Climate scientists believe that the temperature threshold that would bring about the melting of the Greenland icesheet is between 1°C and 3°C, in other words well below the 4.6°C warming level expected under A1F1.

Melting of the Greenland icesheet would eventually result in the world’s oceans rising by around seven meters, dramatically redrawing the geography of the Earth.

A recent study³ concluded that a 4°C rise in the Earth's average temperature would kill of 85% of the Amazon rainforest, and that even a 2°C rise, now seen as unavoidable, will see 20-40% of it dies off.

References:

1. Requiem for a Species – Clive Hamilton

2. IPCC (Intergovernmental Panel on Climate Change)
3. David Adam, 'Amazon could shrink by 85%, die to climate change, scientists say', Guardian, 11 March 2009.