We would like to show the urgent need to act in order to mitigate global warming. For this purpose, we simulate different scenarios for the future emissions of carbon dioxide (CO2) and calculate their effects on the rise of the average temperature on Earth. Information about the simulation model can be found further down at the end of this article.
Let's first repeat some basic facts of global warming:
Let's first look at the "business as usual" scenario. What would happen if we carried on with increasing CO2 emissions and if no measures were taken to mitigate global warming? The prediction of CO2 emissions are taken from "World energy outlook 2006" of the International Energy Agency (IEA) for 2007 until 2030. After 2030, we have extrapolated the trend (see purple curve in graph below).
The blue line indicates the resulting average temperature increase. The red zone with devastating effects on our environment is entered around the year 2060.
Graph 1: Temperature increase in the "business as usual" scenario (no measures against global warming taken)
The world-wide emissions of CO2 for the year 2006 was about 28 billion tonnes. What would happen if we froze the world-wide emissions of carbon dioxide to the current level? Could global warming be mitigated? For this purpose, we simulate a constant emission of 30 billion tonnes of carbon dioxide per year.
The blue curve again shows the effect on the average temperature increase. The increase is less steep than in the example above, but the red zone with temperature increases of more than 2 C is still reached. Devastating effects on our environment can be expected to start around the year 2075.
The world-wide emissions of CO2 for the year 2006 was about 4.5 tonnes per capita. What would happen if we froze the world-wide per capita emissions of carbon dioxide to the current level? Could global warming then be mitigated? For this purpose, we simulate a constant emission of 4.5 tonnes of carbon dioxide per year per capita.The blue curve again shows the effect on the average temperature increase. The increase is surprisingly steep and the red zone with temperature increases of more than 2 C is already reached around the year 2060. So global warming cannot be mitigated with keeping the emissions of CO2 per capita at the current level, either.
Graph 3: Temperature increase with a constant emission of CO2 per capita of 4.5 tonnes per year.
The reason for the strong increase of CO2 emissions even if per capita emissions are kept constant is the growing world population , see graph below. The prediction until 2050 are taken from U.S. Census Bureau, Population Division (http://www.census.gov/ipc/www/). Data last updated 08-24-2006. After the year 2050, a growth of 0.2% per year has been assumed.
Graph 4: Growing world population.
Now let's look at potential solutions to global warming. We call a scenario a "solution" if the red zone with temperature increases of more than 2 C is not entered.
The graph below shows a decrease of world-wide CO2 emissions by 1.9% per year starting with the year 2008 (purple curve). In this scenario it is just possible to stay below a maximum heat up of 2 C (blue curve).
Graph 5: Decrease of CO2 emissions by 1.9% per year to mitigate global warming
What is the effect on the CO2 emissions per capita if the world-wide total CO2 emissions were decreased by 1.9% per year? The graph below shows the average CO2 emissions per capita for a decrease of world-wide CO2 emissions by 1.9% per year starting with the year 2008 (purple curve). The red curve shows the assumed grow of world population (according to U.S. Census Bureau until the year 2050 and 0.2% increase per year thereafter, respectively).
By the year 2050, the average CO2 emissions needed to be reduced to 2 tonnes per capita (current world-wide average is 4.5 tonnes, American average is 20 tonnes and European average is 10 tonnes per year, current CO2 emissions by country ). In the medium and long term, there is no justification for the industrialised world to pollute the Earth more than others. So we should reduce our carbon footprint to 2 tons per capita per year until 2050.
Graph 6: CO2 emissions per capita for a decrease of world-wide CO2 emissions by 1.9% per year
In the last step let's look at the effect of postponing measures to mitigate global warming by 10 years. The graph below shows a potential solution with no measures until the year 2017 (business as usual until 2017 and taking measures later from the year 2018 on). If mankind starts decreasing the emissions of CO2 in the year 2018, a decrease of 2.5% per year is required to avoid the red zone with potentially unimaginable devastating effects on our environment.
Graph 7: Decrease of CO2 emissions by 2.5% per year starting in 2018 to mitigate global warming
It still seems to be possible to avoid the most devastating effects on our environment. However we must start acting immediately. The longer we keep on talking instead of acting, the more drastic measures are needed. However, from past experience we know that the more drastic a measure is, the less likely is its implementation!
Global warming is not about the others, global warming is about us and our personal behaviour . Everyone must bring down his or her personal contribution .
The simulation model used to produce the above graphs has been adapted from a model originally produced by Tony Cooper for the Global Commons Institute in the UK. It is based on data provided by the Hadley Centre. We have released the model as spreadsheet calculation for climate change simulations. It can be downloaded from our webpage.