Hansen et al's paper is here
So let’s have a look at the substance of this paper. What does it say and how does it say it. First of all we should point out that Hansen is only one of its authors. There are 18 authors in total of this paper including Hansen. This is not a one man (or woman) crusade.
One of Hansen et al’s very first points is that there is a difference between what has been previously agreed to (e.g. at Kyoto in Japan) and what is actually happening. And this is that emissions have not decreased over the last 20 years but have actually increased and have done so at a rate that is higher than previously. Specifically at a rate of a 3% increase per year in the 2000-2012 period as opposed to 1.5% increase per year in the 1980 – 2000 period1. It is also pointed out that Governments are approving more resource intensive methods of coal, gas and oil extraction including removal of mountain tops, hydro-fracking and drilling in oceans2. This would seem to be far from the type of Government action that has both been agreed to and is needed to restrict Climate Change to an annoyance rather than a catastrophe.
Hansen et al then go on to describe how global warming is triggered, noting that CO2 has little impact on incoming sunlight but that it makes the atmosphere more opaque at infrared wavelengths causing the radiated heat’s escape to space to occur at a higher level meaning of course that less of it escapes as it heats up more of the atmosphere. It also notes that the world’s oceans have so far taken up most of this CO2 but that in the future they are just as capable of contributing CO2 to the atmosphere. They also mention the energy imbalance and describe how our planet must at some stage return to a condition of energy balance for the warming to cease and for the climate of the Earth to stabilize3. They mention that the measured imbalance in the 2005-2010 period was +0.5860.15 W/m2. Past climate is analyzed and it is noted that although the Pliocene was only about 3 degrees c warmer than the Holocene (our current era, although increasingly we are seeing a change to the Anthropocene) that sea levels were anything up to 25 metres higher than they currently are. It is also noted that sea levels rose by as much as a few metres per century during previous warming periods. The qualifier though is that we are currently warming the planet at a much faster rate than natural cycles have moved in the past. And if we go back to the Eocene we will find a mostly watery planet with little ice. If that were to happen to us, as Hansen et al point out, most of today’s coastal cities would be inundated and of little use to us.
Do we really need to do this? Why are we so addicted to these sources of burnable carbon that we are prepared to continue to operate a business as usual approach to carbon extraction despite declining ease of access, increasing costs and a higher resource use when compared to the gain in stored carbon that is attained? As Hansen et al point out, the amount of land required per barrel of oil produced in Alberta Canada has risen 12 fold between 1955 and 2005. Hansen et al also point out that Fossil Fuels do not pay the full costs of their extraction to society while at the same time they receive large Government subsidies.
So what could happen if, as it is clear we are currently doing, we do not move to more carbon neutral or even carbon negative energy systems? One of the most obvious changes will be at our shorelines where over the next 100 years we could see anything from several tens of centimetres to several metres of Sea Level Rise. There will also be species extinction associated with any rise in temperature of both the oceans and atmosphere. Hansen et al put this potential mass extinction at up to 52% of current species depending on the level of increased temperature. Naturally there will also be food shortages as some animals and plants find it difficult to adapt to a new climate that may in fact keep changing for quite a while before it stabilizes. Hansen et al also mention challenges to maintaining human health including a rise in infectious diseases, shortages of water and changes to the type of plants that may exist. They state that “Global warming of 2C would be well outside the Holocene range and far into the dangerous range”.
Obviously this should be, as best as we possibly can, avoided. It is quite common for people in industry to suggest CO2 mitigating technologies as a possible solution. But most of these supposed technologies do not currently exist and if they did their costs would still be very large. Hansen et al estimate the cost at something approaching 30 trillion dollars, or $90,000 per individual for the United States. Storing the carbon as carbonate bricks also presents a storage problem as they are of little use for building so the United States would have to store the equivalent 66,000, more or less unusable, brick made Great Pyramids of Giza. Hansen et al state that “CO2 must be reduced to about 345 ppm to restore energy balance. It is clear what Hansen et al think needs to happen as they also state that “It is instructive to see how fast atmospheric CO2 declines if fossil fuel emissions are instantly terminated”. The suggested route to this is with a carbon tax which Hansen et al suggest could be agreed between the two largest emitters, the United States and China, who will effectively pull everyone along with them by carrot and stick one would assume, the carrot is mentioned as effectively favouring trading nations which are attending to emission guidelines.
This information forms the basis for the final arguments that today’s (and tomorrow’s) children are having an injustice piled onto them and that they effectively should be able to claim the cost from the current generation. They suggest that the atmosphere could be thought of as a public trust (and in this respect recent decisions in law in New Zealand have given some natural assets the legal rights of a legally defined person). They go on to state that although our grandparents could claim ignorance the present generation don’t have that defense and can only pretend that we didn’t know. Kyoto is mentioned as an example of a climate agreement not achieving a lasting outcome and that to continue to operate on the same basis will virtually guarantee a climate injustice. Can you disagree?
So as anyone interested can easily follow up on the information contained in this short essay, I have taken the original references directly from Hansen et al’s own references rather than point readers to the different parts of the Hansen et al where the relevant information has been given.
- BP Statistical Review of World Energy 2012, https://web.archive.org/web/20160312083658/https://www.bp.com/en_no/norway/media/press-releases-and-news/2012/bp-statistical-review-of-world-energy-2012.html (the original link was broken), retrieved 28th July 2019.
- Boden TA, Marland G, Andres RJ (2012) Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2012.
- Hansen J, Sato M, Kharecha P, Beerling D, Berner R, et al. (2008) Target Atmospheric CO2: Where Should Humanity Aim? The Open Atmospheric Science Journal 2: 217–231.
- Hansen J, Sato M, Kharecha P, Schuckmann K (2011) Earth’s Energy Imbalance and Implications. Atmos Chem Phys 11: 1–29.
- Foster GL, Rohling EJ (2013) Relationship between sea level and climate forcing by CO2 on geological timescales. Proc Natl Acad Sci USA doi:10.1073/pnas.1216073110.