Where shall we go from here?
(or “Climate science in a nutshell – Part 4”)
This will be the last of my posts on the scientific basis for concern over anthropogenic climate change based on James Hansen’s Storms of my Grandchildren. Although, I am barely half way through it, it is stuffed full of information everyone should know and I would not want to stop you reading the book yourself because you think you know what it says. Therefore, after today, I will just post one more item based on its content (regarding Richard Lindzen’s prominent role in perpetuating prevarication) and that will be it.
So, to summarise the story so far, Hansen was one of the first to use models to aid our understanding of the mechanics of the atmosphere, but sees palaeoclimatic study as the key to understanding what we are doing to our planet, and blames special interests [i.e. the fossil fuel lobby (FFL)] for interfering in politics and persuading politicians to second-guess (or ignore) science and scientists. (For those that are interested, this is the focus of Mark Bowen’s Censoring Science: Inside the Political Attack on Dr. James Hansen and the Truth of Global Warming, which you can hear both Hansen and Bowen discussing here.) For example, on first becoming President in 2001, Bush had said (in his first Rose Garden speech) that his administration would treat CO2 as a pollutant and “be flexible to adjust to new information”. Whereas, in point of fact, he broke that promise within two months of taking office and spent the rest of his eight years in power ruthlessly suppressing inconvenient information. Furthermore, on more than one occasion, Hansen asserts that our problem is that government Energy departments around the world seem to believe it is a “god-given fact that humanity will proceed to burn all fossil fuels”. Whereas, even though it seems easier to get someone to stop picking their nose, we must stop burning fossil fuels.
There are actually two kinds of palaeoclimatic evidence upon which Hansen relies to reach this conclusion. These are (1) ice core data (covering less than the last million years); and (2) sea floor sediment data (covering the last 65 million years). However, the really clever bit of Hansen’s analysis has been to interpret the CO2 and temperature (i.e. oxygen isotope) data derived from the latter by reference to what we know about plate tectonics and the positions of the continents at any given point in geological time. Thus, he shows that the rise in the Earth’s global average temperature between 60 and 50 million years ago was due to the subduction of large amounts of carbonate seafloor sediments as India approached Asia. Conversely, the fall in global average temperature between 50 and 35 million years ago was due to the collision causing the formation and subsequent erosion of the Himalayas. The precise mechanisms for introducing CO2 to – and removing it from – the atmosphere are complicated, but it should be borne in mind that there is no other explanation that fits the facts: The Sun’s overall energy output has risen by less than 0.5% over the last 65 million years, whereas the natural forcings known to have caused the glacial – interglacial oscillations of the last 1 million years have only become effective in the absence of other factors and operate over much shorter timescales.
So where does that leave us today? Well, up until about 4 years ago, Hansen was convinced that humanity should aim to keep atmospheric CO2 below 450ppm (the conditions which induced Antarctica to become glaciated 35 million years ago). However, Hansen has since revised the safe limit down to 350ppm (compared to the current level of 390ppm) to which we must somehow return the atmosphere. Why has he done this? Well, the detail is in Hansen et al (2008) but, the main reasons are based on the (now familiar?) observation of thawing permafrost; melting sea ice, mountain glaciers and ice sheets; bioclimatic zone migration, and dying coral reefs. Some of these are simply threats to biodiversity but some are evidence of the amplifying feedbacks that threaten to accelerate change way beyond human ability to control, mitigate, or adapt: If we allow CO2 to reach 450ppm we will be unlikely to stop it continuing to rise to 650ppm, which would invoke sea level rise 1-2 metres per century for several centuries; and an eventual rise in temperature of at least 6 Celsius (i.e. until the Earth’s energy balance is eventually restored). In other words, an end to civilisation as we have known it for 7,000 years.
Hansen believes we can still avert disaster but only if we can derail the misinformation campaign being waged by those in favour of “business as usual“; and refuse to accept the greenwash being promulgated by even the greenest of governments. Hansen is quite blunt. He seems to believe that all governments (with the possible exception of Iceland) are in denial about the consequences of burning all fossil fuels simply because we can; and in denial about our ability to stabilise “greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” (Article 2 of the UNFCCC) simply because we are already doing exactly that. Certainly, the UK government has already failed this reality test by allowing Cairn Energy to drill for oil in the Arctic, whereas President Obama faces his moment of decision in the next few days: Will he approve or refuse permission for the Keystone XL Pipeline?
Clive Hamilton says that anthropogenic climate change is a “failure of modern politics” but I think it is collective “failure of imagination” and/or a “classification error”. We just don’t seem to be able to grasp the potential consequences of our current actions (or don’t want to accept the reality of them). Quite what historians will make of it, and how many people will be left to read what they write, no-one seems to care. It is the ultimate human folly: Everyone seems too busy exercising their right to “Carpe Diem” to stop and ask “Quo Vadis?”…