Climate Change: A return to the past

In "the 11th hour," the authors describe the history of earth as a 12 hour clock.  Here they discuss the recent arrival of humans in the last two seconds and how in the last 100 years, a nanosecond of geologic time, we've changed the atmospheric carbon from 300 PPM to 400 PPM; a 35% increase.  They then frame the ramifications into an apocalyptic doomsday...that if we do nothing then perhaps we will face a stagnant ocean that recreates the Permian extinction that destroyed 96% of life on the planet.  Or maybe a conversion of our beloved Earth to the hellishly hot acid rain filled landscape of Venus.  Or even a conversion to the barren lifeless planet of Mars.  Perhaps a little of all three?  The authors of the video seem to be unaware that 45 geologic minutes ago the earth's atmospheric CO₂ was above 1000 PPM.

Paleobotanical and herbaceous macrofossil analysis of the time period from 34 - 64 million years ago (MYA) definitively demonstrate that the world did not end, the oceans didn't boil, there wasn't a carbon cycle cascade that plunged the earth into a Venus like nightmare, no dominance of low altitude oceanic clouds creating a cooling cascade into a snowball earth, and there wasn't a mass extinction; despite maximum atmospheric CO₂ almost hitting 2000 PPM.  In fact life was thriving during this time, as adaptive radiation was rapidly evolving the survivors of the 65 MYA meteor to become the animals of today.

Various mammal species that existed during the Paleocene and Eocene epochs.  BBC

Then at around 30 MYA atmospheric CO2 started to decrease rapidly; hitting a low of 200 PPM around 10 MYA.  The majority of our plants today have evolved in a high carbon dioxide environment.  Once CO₂ dropped below 500 PPM many of these plants became carbon stressed.  Flowering plants had never encountered CO₂ levels this low since they evolved 200 million years prior.  Because of this, a new photosynthetic pathway (C4 photosynthesis) was independently evolved over 60 times across dozens of Angiosperm taxa.  It was also during this time of low atmospheric CO2, this aberration of earth's history, that humans evolved.

A C4 dominated Grassland.  The Nature Conservancy's Niobrara Valley Preserve. 

All this to say that there is a practical side to understanding climate change.  The planet has changed before and though the current change is rapid, most plants are "already" adapted to a high CO2 environment (C3 plants), and the new C4 plants are perfectly adapted to increasing variability in precipitation and temperature.  Vegetation assemblages and suitable habitats will change and plants will need to migrate, but they can and do migrate deceivingly fast; as they have numerous times in the past.  Juniper woodlands have expanded their entire extent by 90% in the last 100 years and it only took the invasive weed Cheatgrass 30 years to completely dominate the intermountain west.  

Migrating trees.  Probably invasive.

  That's not to say that we don't have anything to worry about, but enough with the hyperbole, the fear mongering, and the needless exaggerations.  We are not doomed, all life is not going extinct, and the world is not going to implode.  Most life on this planet has evolved in a high CO₂ environment, but we have not and life has not had much time to evolve with us.  Many of the issues we currently face such as resource use, population size, and food  and water availability are exacerbated in a changing climate; but would otherwise still be continuing problems without climate change.  The human induced mass extinctions of this age will continue with or without climate change as well, but is definitely made worse as the need to migrate increases and migrating corridors and habitats are converted to condos.  Many negative scenarios described in the film, if you pull away from the more extreme rhetoric and hyped up emotion, will be real challenges in the future.  

Practically speaking, change is something that does need to happen.  The negative influence of climate change on all the issues we are already facing, and the new issues climate change brings to the table, does mean that we can't ignore this problem.  However, we should look at the problem analytically and avoid the emotion based knee jerk reactions that so often seem to dominate the discussion and cloud decisions.  As we move towards 9 billion people, and as the resource demands of people worldwide increases, there are going to be dramatic challenges that need to be faced; challenges that can be overcome. Life will continue, but how humans proceed into that uncertain future is up to us.