What are greenhouses gases and how do they impact on the climate?

IPCC: to avoid more than 2 degrees temp increase, emissions should reach a maximum of 44 gigatonnes of CO2 by 2020, falling to 40 gigatonnes by 2025 and further to 22 gigatonnes by 2050.

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Emissions per capita in metric tonnes CO2/year      
  1990 2005 2010 2030 2030
USA 19.30 19.60 17.56 11.56 -41%
Canada 15.70 17.40 14.68 12.18 -30%
China 2.20 4.40 6.20 1.76 -60%
UK 9.70 9.00 7.86 4.68 -48%
European Union 8.10 8.10 7.35 5.35 -34%
Australia 15.50 17.20 16.70 12.73 -26%
Netherlands 10.60 10.50 10.96 6.30 -40%
Japan 8.90 9.70 9.19 7.28 -25%
Germany 11.60 9.70 9.12 5.24 -46%
France 6.40 6.20 5.56 3.72 -40%
Indonesia 1.80 1.50 1.803 1.88 25%
New Zealand 7.10 8.20 7.22 5.74 -30%
World 4.60 4.60 4.88 N/A N/A
OECD 11.00 11.00 10.15 N/A N/A
Russia 14.00 11.30 12.23 N/A N/A
India 1.80 1.30 2.67 N/A N/A
           
Sources:  
1990, 2005, 2010 Worldbank  
2030: target
compared to 2005:
 
EU: compared
to 1990 (Climate Council)
 
IPCC:
to avoid more than 2 degrees temp increase, emissions should reach a maximum
of 44 gigatonnes of CO2 by 2020, falling to 40 gigatonnes by 2025 and further
to 22 gigatonnes by 2050.