Needed Change
So what do we need to do? Simply put, stop emitting CO2 and other greenhouse gases. It’s easily said, but requires a major change to our energy technology, and is fiercely resisted by some of the largest companies in the world who would lose out in the transition. So far no government has had the guts to make anything like the necessary changes. To compound the problem the western world is responsible for most of the historical emissions while the emerging countries, especially China who is now the world’s largest emitter, are growing rapidly. Both need to change rapidly but are locked in an argument about who should do what.
There are two ways determining what is “safe”. For most of the past 10,000 years CO2 concentrations in the atmosphere have been around 280 parts per million, so this can be assumed to be safe. We are now close to 400ppm and weather patterns are definitely changing and Arctic ice is in decline so it is thought that this is not a safe long term level. James Hansen, one of the most respected climatologists, believes that 300 – 350ppm can be considered a safe target. As we therefore need to reverse the 2.3ppm annual increase this begs the question “how quickly must we reduce concentrations to a safe level?”
CO2 remains in the atmosphere for a long time (centuries) and methane the other major greenhouse breaks down to CO2 and so scientists believe that the important metric is total emissions since the beginning of the industrial revolution, and this can be used to determine the temperature rise likely. Most believe that a temperature rise of more than 2o is likely to trigger various feedbacks which will rapidly drive temperatures higher beyond our control. The limit is not well established and a significant number of scientists believe we should use 1.5o instead. Most governments and the UN have adopted 2o as the safe limit.
Two studies led by Myles Allen and Malte Meinshausen show that total cumulative emissions of CO2 must be kept to 3,670 billion tons to keep the temperature rise to less than 2o though this still leaves a 5% chance of reaching 3.9o!. Note that emissions are commonly measured in two ways, either in tons of Carbon or in tons of Carbon Dioxide (one ton of carbon = 3.67 tons of carbon dioxide). We have already emitted more than half of this, and we are emitting over 30 billion tonnes CO2 per year and will use up our allowance in roughly 40 years at our current rate of increase. We must limit future emissions to 2,750 billion tons CO2 to have a 67% chance of staying under 2o. However the industrialised countries have not only more responsibility for past emissions but their per capita emissions are higher than other countries. Jim Giles put together this video showing how emissions need to fall if each person on earth were given a fair share. The US (and Australia’s) share would run out in about 6 years at current rates, Europe in 12 and China in 24 years.
Quite separately A Friends of the Earth report looks at what would be required to have a 70% chance of limiting warming to 2o which would require worldwide emissions to fall by 16% by 2030 based on 1990 levels. This would require the US to slash its emissions by as much as 95% by 2030, the EU by 83%, and the UK by 80% and China would need to peak its emissions by 2013 and then reduce them by 5% per year.
Obviously neither of these looks possible politically.
The scheme world leaders are adopting to share out emissions cuts is called contraction and convergence which ends up with each person in the globe allowed to emit the same amount of CO2 at the end of the period (normally 2050). Therefore developing countries could continue to increase emissions until they are at that level. Note that this takes no notice of historical emissions which were due to the developed countries. As the world population is projected to rise almost 50% to 9 billion by 2050 each person’s slice of the pie will reduce over that period.
So clearly very few countries (if any) are doing anywhere near enough. But what exactly can we do to reduce emissions? Joe Romm of Climate Progress has been updating the idea developed in Princeton University of “stabilization wedges”. Each of these wedges is some initiative which ultimately reduces emissions by a total of 1 billion tons of carbon per year (3.67 GtCO2). These obviously start at no reduction and build up to the full reduction over some decades. Even the rather staid International Energy Agency comes to similar conclusions. His list of the proposed reductions is:-
- <1 wedge of albedo change through white roofs and pavement (aka “soft geoengineering) — see “Geoengineering, adaptation and mitigation, Part 2: White roofs are the trillion-dollar solution“
- 1 wedge of vehicle efficiency — all cars 60 mpg, with no increase in miles travelled per vehicle.
- 1 of wind for power — one million large (2 MW peak) wind turbines
- 1 of wind for vehicles –another 2000 GW wind. Most cars must be plug-in hybrids or pure electric vehicles.
- 3 of concentrated solar thermal (aka solar baseload) ~5000 GW peak.
- 3 of efficiency — one each for buildings, industry, and cogeneration/heat-recovery for a total of 15 to 20 million GW-hrs. A key strategy for reducing direct fossil fuel use for heating buildings (while also reducing air conditioning energy) is geothermal heat pumps.
- 1 of solar photovoltaics — 2000 GW peak
- 1 wedge of nuclear power – 700 GW
- 2 of forestry — End all tropical deforestation. Plant new trees over an area the size of the continental U.S.
- 1 wedge of WWII-style conservation, post-2030 [this could well include dietary changes]
As you can see this is a massive undertaking, even though it takes place over 30 to 40 years. However in his article Joe shows that it is achievable with the technology we have now, plus that which is likely to be commercialised over that period, and is possible at a reasonable cost. Many organisations and studies have come to the same conclusion, from the IPCC to the Stern review.
The obvious conclusion of the cumulative emissions discussion above is that the sooner we get on with it the less it will cost us.
