Running the numbers

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

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.

According to the “Carbon Footprint of Nations” website, covered on Simple Climate back in March, emissions per person in the UK in 2001 were 15.6 tonnes per year. The US racks up 28.6 tonnes per person per year, whereas the figure for India is just 1.8 tonnes, and China is 3.1 tonnes. Notably under the Carbon Footprint of Nations classification, just 1 tonne per person per year is seen as the sustainable level of CO2 consumption.

A return flight from the UK to the US might produce 1.5 tonnes of CO2, but because airliners emit their CO2 directly into the upper atmosphere, this has a much greater impact on global warming. Estimates vary that the impact is multiplied by between 2 and 3, with 2.7 being the factor normally used in carbon calculators, which would make a UK-US trip produce the equivalent of 4 tonnes of CO2 released at ground level. So for a UK citizen to cut their CO2 emissions to the level that is likely to be necessary to keep temperature rises below 2°C, they need to travel to the US about 3½ times less each year. Of course most UK citizens don’t fly that far, that often. So what options are open to them? Other alternatives include switching electricity supplies to a 100% green energy tariff, which would save around 2 tonnes of CO2 emissions per household per year.

As you may have gathered, I live in the UK, where there will be an election tomorrow. While there are options open to individuals, the emissions cuts needed to combat global warming require commitment on a national level. I will be voting for the Green Party, although they they object to nuclear energy, which I see as a crucial weapon in the fight against climate change. In fact, on the nuclear and renewable energy basis, my own environmental beliefs lie closer to those of the existing Labour government. So, despite the need for change in my country, because of their admirable combination of pragmatism and determination when it comes to global warming, part of me hopes that Labour retains power.

In 2008, humans across the world were responsible for emitting greenhouse gases equivalent to 46 billion tonnes per year of CO2. In that year there were 6.7 billion humans on the planet. On average, each human on the planet was therefore responsible for the equivalent of 6.9 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 5.8 tonnes per person.

The Kyoto protocol and subsequent negotiations have focussed on 1990 as the base year from which to reduce emissions. Estimates suggest that in that year greenhouse gases equivalent to 36 billion tonnes of CO2 were emitted. Just hours 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, or a total figure of just 18 billion tonnes 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.

According to the “Carbon Footprint of Nations” website, covered on Simple Climate back in March, emissions per person in the UK in 2001 were 15.6 tonnes per year. The US racks up 28.6 tonnes per person per year, whereas the figure for India is just 1.8 tonnes, and China is 3.1 tonnes. Notably on the Carbon Footprint of Nations dial of consumption, just 1 tonne per person per year is seen as the sustainable level of CO2 consumption.

A return flight from the UK to the US might produce 1.5 tonnes of CO2, but because airliners emit their CO2 directly into the upper atmosphere, this has a much greater impact on global warming. Estimates vary that the impact is multiplied by between 2 and 3, with 2.7 being the factor normally used in carbon calculators, which would make a UK-US trip produce the equivalent of 4 tonnes of CO2 released at ground level. So for a UK citizen to cut their CO2 emissions to the level that is likely to be necessary to keep temperature rises below 2°C, they need to travel to the US about 3½ times less each year. Of course most UK citizens don’t travel that often. So what options are open to them? Other alternatives include switching electricity supplies to an 100% green energy tariff, which would save around 2 tonnes of CO2 emissions per household per year.

As you may have gathered, I live in the UK, where there will be an election tomorrow. While there are options open to individuals, the emissions cuts needed to fight change require determination on a national level. I will be voting for the Green Party, although they they object to nuclear energy, which I see as a crucial weapon in the fight against climate change. In fact, on the nuclear and renewable energy basis, my own environmental beliefs lie closer to those of the existing Labour government. So, despite the need for change in this country, because of their admirable combination of pragmatism and determination when it comes to climate change, part of me hopes that Labour retains power.

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3 Responses to “Running the numbers”

  1. A picture of climate change is worth 1,000 words « Simple Climate Says:

    […] above image was first published on this blog in this entry. Climate models also suggest that by 2039, most of the U.S. could experience at least four seasons […]

  2. andyextance Says:

    In fact, checking back, this is wrong. Total CO2 emissions reached 36.7 billion tonnes in 2010 and population was 6.9 billion, giving an average of 5.3 tonnes per person. That gives the impression that we don’t have to worry too much about the 2020 target of 5.8 tonnes per person, but it’s worth remembering that to bring climate change under control by 2100, models suggest we need to reduce CO2 emissions to zero.

  3. Hope from a surprising source that consumption can be controlled « Simple Climate Says:

    […] how much do we need to cut our consumption by? When I first started this blog, I tried to do the numbers on how much we needed to reduce our fossil fuel consumption per person – but checking back, I got […]


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