Bru Pearce Blogs
The earth is a highly dynamic planet; it changes dramatically over the billions of years of geological time, continents drift apart and come together. The gradually increasing brightness of the sun, changes in the orbit of the earth around the sun and moon around the earth, are all causes that have had the effect of making the biosphere (all living things) change and adapt. Those adaptations extend right out to promoting atmospheric changes to maintain environments suitable to support life.
Over shorter time scales of 100,000 years or so, changes in earths tilt towards the sun takes us in and out of ice ages. The last ice age ended quite rapidly about 20,000 years ago that is to say it took about 8,000 years for CO2 levels to rise from 180 ppm to 280 ppm and for the earth’s average temperature to increase by 6-8 C for us to arrive at the start of the present interglacial Holocene.
It then took 12,000 years for man to arrive at the start of the industrial revolution. Since then man has been burning fossil fuels at an ever increasing rate. So that now atmospheric CO2 levels are at 397 ppm. Loosely speaking we have raised atmospheric CO2 in 80 years further than the natural tilt of the pole towards the sun did in 8,000 years, which is more than sufficient change to counter the slow decent into the next ice age which without man would be starting some time soon.
But it’s not that simple, we would not be in the grip of a full ice age for at least another 25,000
years, so we have made a massive over correction! Our CO2 levels have already set the planet up for another 3-4 C of warming and we keep pushing CO2 and other green house levels up. There is no historical president in earth’s history with the current continental configuration and sea levels for such high levels of green house gasses in the atmosphere, so we are moving into unknown territory.
So far we are only just beginning to see the consequences of what we have done, as the inertia in the earth systems and in particular additional energy absorbed by the oceans takes time to have effect and for the feedback loops to kick in and accelerate.