Continued growth in CO2 emissions could lead to dangerous global temperature rises. The red lines represent a “business as usual” scenario that we might already be following, while the blue lines are what is needed to keep emissions below the dangerous 2°C level. Credit M. Meinshausen
In 2008, 2010 humans across the world were responsible for emitting greenhouse gases equivalent to 46 37 billion tonnes per year of CO2. In that year there were 6.7 6.9 billion humans on the planet. On average, each human on the planet was therefore responsible for the equivalent of 6.9 5.3 tonnes of emissions. Joeri Rogelj, who spoke to Simple Climate last week, suggests that by 2020 emissions should not exceed the equivalent of 44 billion tonnes per year of CO2. By that time the UN anticipates the world population reaching 7.6 billion, in its medium-growth level prediction scenario. This would mean a cut in emissions to of 5.8 tonnes per person.
The Kyoto protocol and subsequent negotiations have focussed on 1990 as the base year from which to reduce emissions. Rogelj and his colleagues estimate that in that year greenhouse gases equivalent to 36 billion tonnes of CO2 were emitted. Until shortly before the end of the negotiations for the Copenhagen Accord in December, the draft agreement still contained targets specifying a global reduction of 50% below 1990 emissions levels by 2050. This would amount to just 18 billion tonnes of CO2 emissions annually. These kind of targets are seen as necessary for keeping global temperature rises below the 2°C level beyond which climate change would be dangerous. In 2050, the UN’s medium population growth scenario predicts 9 billion people on the planet, meaning that average emissions per person would be just 2 tonnes per year. Read the rest of this entry »
