“The implication of our study is that elevated CO2 is sufficient to lead to inhospitable conditions for marine life and excessively high temperatures over land would contribute to the demise of terrestrial life.”
WHO: Jeffrey T. Kiehl, Christine A. Shields, Climate Change Research Section, National Center for Atmospheric Research, Boulder, Colorado, USA
WHAT: A complex climate model of atmospheric, ocean and land conditions at the Permian mass extinction 251 million years ago to look at CO2 concentrations and their effect.
WHEN: September 2005
WHERE: Geological Society of America, Geology vol. 33 no. 9, September 2005
The largest mass extinction on earth occurred approximately 251million years ago at the end of the Permian geologic era. Almost 95% of all ocean species and 70% of land species died, and research has shown that what probably happened to cause this extinction was carbon dioxide levels.
As the saying goes; those who do not learn from history are doomed to repeat it, so let’s see what happened to the planet 251 million years ago and work out how we humans can avoid doing it to ourselves at high speed.
This research paper from 2005 did the first comprehensive climate model of the Permian extinction, which means their model was complicated enough to include the interaction between the land and the oceans (as different to ‘uncoupled’ models that just looked at one or the other and not how they affected each other).
The researchers used the CCSM3 climate model that is currently housed at the National Centre for Atmospheric Research (NCAR) and is one of the major climate models currently being used by the IPCC to look forward and model how our climate may change with increasing atmospheric carbon pollution (or emission reduction). They organised their model to have ‘realistic boundary conditions’ for things like ocean layers (25 ocean layers for those playing at home), atmospheric resolution and energy system balance. They then ran the simulation for 900 years with current conditions and matched it with observed atmospheric conditions and got all of their data points correct with observed data.
Then, they made their model Permian, which meant taking CO2 concentrations and increasing them from our current 397ppm to 3,550ppm which is the estimated CO2 concentrations from the end of the Permian era.
What did ramping up the CO2 in this manner do for the planet’s living conditions in the model? It increased the global average temperature to a very high 23.5oC (the historic global average temperature for the Holocene (current era) is 14oC).
Changing the CO2 concentrations so dramatically in the model changed the global average ocean surface temperature 4oC warmer than current conditions. Looking at all the ocean layers in their model, the water was warmer in deeper areas as well, with some areas at depths of 3000m below sea level measuring 4.5-5oC where they are currently near freezing.
The greatest warming in the oceans occurred at higher latitudes, where ocean temps were modelled at 8oC warmer than present, while equatorial tropical oceans were not substantially warmer. The oceans were also much saltier than they currently are.
The big problem for all of the things that called the ocean home at the end of the Permian era is the slowing of ocean circulation and mixing. Currently, dense salty water cools at the poles and sinks, oxygenating and mixing with deeper water allowing complex organisms to grow and live. If this slows down, which it did in this model, it has serious consequences for all ocean residents.
Their Permian model measured ocean overturning circulation around 10 Sv (million cubic metres per second), whereas current ocean overturning circulation is around 15-23 Sv. The researchers think the ocean currents could have slowed down enough to create anoxic oceans, which are also known as ‘ocean dead zones’ or ‘Canfield Oceans’, and stated that it set the stage for a large-scale marine die off.
If the end of the Permian was pretty nasty for ocean residents, how did it fare for land-dwellers? What happened to the tetrapods of Gondwanaland? Well it looked really different to how earth looks today.
There were deciduous forests at high latitudes, and the elevated CO2 in the model was the dominant reason for warm, ice free Polar Regions (which also hindered ocean circulation). Land surface temperatures were between 10 – 40oC warmer than they are today. In their model, dry sub-tropical climates like the Mediterranean or Los Angeles and Southern California were much hotter, with the average daily minimum temperatures around 51oC. Yes, Los Angeles, your overnight low could be 51oC.
Understandably, the authors state that ‘these extreme daily temperature maxima in these regions could contribute to a decrease in terrestrial flora and fauna’, which is scientist for ‘it’s so damn hot outside nothing except cacti can grow’.
All of these changes were run over a 2,700 year period in the model, which if you take the 2005 CO2 concentration of 379ppm as your base is an increase of 1.17ppm per year.
This is the important bit to remember if we’re going to learn from history and not go the way of the Permian residents. Our current rate of increase in CO2 concentrations is 2ppm per year, which means we are on a super speed path to mass extinction. If we continue with business as usual, which has been aptly renamed ‘business as suicide’ by climate blogger Joe Romm, we will be at the end of the next mass extinction in around 1,500 years.
All we need to do to guarantee this being the outcome of all of humanity is keep the status quo and keep burning fossil fuels and the entire sum of humans as a species on this planet will be a tiny geological blip where we turned up, became the most successful invasive species on the globe, burned everything in sight and kept burning it even when we knew it was killing us.
However, I think this part from the paper’s conclusion should give most of us a pause for thought;
‘Given the sensitivity of ocean circulation to high-latitude warming, it is hypothesized that some critical level of high-latitude warming was reached where connection of surface waters to the deep ocean was dramatically reduced, thus leading to a shutdown of marine biologic activity, which in turn would have led to increased atmospheric CO2 and accelerated warming.’
As a species, if we are going to survive we need to make sure we do not go past any of those critical levels of warming or tipping points. Which means we need to make sure we stop burning carbon as fast as possible. Otherwise, T-Rex outlasted us as a species by about two million years which would be kinda embarrassing.