 |
| Picture from: http://sharondelgado.org/ |
The global warming
train is an analogy of our current state of affairs. Picture yourself
on a temporally travelling train, which you board at the beginning of
the industrial revolution. As the train travels it produces
emissions, waste products that reflect the anthropogenic pollution
produced worldwide. This in turn causes global warming and thus it
can be known as the 'global warming train'.
Now I must define the last stop. This is some point in time where we really have to stop our addition to global warming. We can't be sure when this will be. It might be soon. It might have already passed. What happens if we have missed it? Well if you miss the last stop, there is no turning back.
The last stop could be scientifically defined as a planetary boundary, particularly that of climate change. In Rockstom et al's paper from 2009 a planetary boundary is defined as “the safe operating space for humanity with respect to the Earth system”. For climate change in particular, the boundary is based on two measurements. These are the global carbon dioxide level, mentioned in my first post, which has the threshold of 350ppm and that of radiative forcing, a measure of the rate of change of energy per unit area. The threshold for radiative forcing is 1 watt per square metre above pre-industrial levels.
We have already surpassed both of these figures and no irreversible reactions have been observed as yet. This may be because, due to the many uncertainties surrounding the planetary boundary, these values are an underestimate of how much damage we can do before irreversible changes occur. This doesn't mean we should keep going however; the irreversible change could well be disastrous.
An important part of this major change will be the reinforcing feedback. Lenton et al's paper on tipping elements reviews the major areas that could potentially tip with the ongoing anthropogenic forcing of global temperatures. This includes the melting of ice sheets and reduction of vegetation which would decrease the albedo of Earth and increase the amount of heat absorbed. Another problem with melting permafrost is the potential release of methane clathrates, a solid form of methane trapped within the ice. The release of large amounts of methane would have devestating results on the global climate. This is one of the theories for the cause of the PETM mass extinction.
Now I must define the last stop. This is some point in time where we really have to stop our addition to global warming. We can't be sure when this will be. It might be soon. It might have already passed. What happens if we have missed it? Well if you miss the last stop, there is no turning back.
The last stop could be scientifically defined as a planetary boundary, particularly that of climate change. In Rockstom et al's paper from 2009 a planetary boundary is defined as “the safe operating space for humanity with respect to the Earth system”. For climate change in particular, the boundary is based on two measurements. These are the global carbon dioxide level, mentioned in my first post, which has the threshold of 350ppm and that of radiative forcing, a measure of the rate of change of energy per unit area. The threshold for radiative forcing is 1 watt per square metre above pre-industrial levels.
We have already surpassed both of these figures and no irreversible reactions have been observed as yet. This may be because, due to the many uncertainties surrounding the planetary boundary, these values are an underestimate of how much damage we can do before irreversible changes occur. This doesn't mean we should keep going however; the irreversible change could well be disastrous.
An important part of this major change will be the reinforcing feedback. Lenton et al's paper on tipping elements reviews the major areas that could potentially tip with the ongoing anthropogenic forcing of global temperatures. This includes the melting of ice sheets and reduction of vegetation which would decrease the albedo of Earth and increase the amount of heat absorbed. Another problem with melting permafrost is the potential release of methane clathrates, a solid form of methane trapped within the ice. The release of large amounts of methane would have devestating results on the global climate. This is one of the theories for the cause of the PETM mass extinction.
 |
The Pie chart really
puts the importance of tipping elements into perspective.
Picture from: http://www.ees.lanl.gov/ees6/clathrates/images/Fig3.gif |
It would appear that we have not missed the last stop, but we must be getting close. I agree with Lenton that we are most likely being lulled into a false sense of security by current global warming models that do not take into account tipping elements. Let's stop being the passengers and start being the drivers, before it's too late.
No comments:
Post a Comment