IPCC declares global warming unequivocal
In an ongoing development of one of the largest and most in-depth scientific undertakings to date, the nobel prize award-winning Intergovernmental Panel on Climate Change has declared that global warming is primarily caused by human activity and that a robust response by humanity would "cost" our economies a mere 1.2% of economic growth. It has already been shown that greenhouse gas levels are higher than they have been for at least 600,000 years. That means that no homo sapiens has experienced, nor has any human civilization existed in, the climate we are about to enter. You have to go back before cities, before agriculture, past many ice age cycles - indeed to the days of homo erectus - to find a climate as warm as the one we have now caused, and which our children and grandchildren are now forced to accept.  This is why the Green Institute considers the situation to be a climate crisis.
 

Table SPM.4: Estimated global macro-economic costs in 2030a) for least-cost trajectories towards different long-term stabilization levels.b), c)

Stabilization levels
ppm CO2-eq)
Median GDP reductiond)
(%)
Range of GDP reductiond) e),
(%)
Reduction of average annual
GDP growth ratesd), f)
(percentage points)
590-710 0.2 -0.6-1.2 <0.06
535-590 0.6 0.2-2.5 <0.1
445-535(g) not available <3 <0.12

Notes:
a) For a given stabilization level, GDP reduction would increase over time in most models after 2030. Long-term costs also become more uncertain. [Figure 3.25]
b) Results based on studies using various baselines.
c) Studies vary in terms of the point in time stabilization is achieved; generally this is in 2100 or later.
d) This is global GDP based market exchange rates.
e) The median and the 10th and 90th percentile range of the analyzed data are given.
f) The calculation of the reduction of the annual growth rate is based on the average reduction during the period till 2030 that would result in the