This is another note in a series about aspects of the climate crisis.
CLIMATE TIPPING POINTS
To postulate climate futures, since repeatable experiments are not possible, climate scientists use what is known about past climate variation to create computerized models. Participants in the Intergovernmental Panel on Climate Change (IPCC) use the results of many such models to reach consensuses about climate futures and appropriate mitigation and adaptive policies. One major criticism of such models is that, until recently, those computer models have not taken sufficient account of amplifying feedbacks in climate systems and that those amplifying feedbacks can, over time, result in reaching tipping points beyond which climate processes take on a life of their own with no longer any possibility of turning back. Amplifying feedback loops and the related concept of Tipping Points are the focus of this note.
These crudely-drawn and over-simplified graphics show amplifying feedback loops that are affecting just three earth systems of critical importance. For each of the three, (and for systems not shown), the key for stopping the feedback is to slow or stop the warming. What is not shown is that, as processes move around the circles, effects are intensifying and may reach a tipping point after which there can be no turning back and the processes spin out of control.
Led by Britain’s Tim Lenton at Exeter University, scientists have identified sixteen such Earth systems that are possible or likely tipping points. While no one knows when specific tipping points might happen, it is likely that, as Earth’s temperature increases from pre-industrial levels, probability of reaching points of “no turning back” increases. Global warming is rapidly closing in on 1.5oC and even 2oC is on the horizon possibly as little as 15 years later. At our current Earth temperature, West Antarctic/Greenland Ice Sheet collapse, Arctic Winter Ice collapse, Boreal Permafrost thawing and coral reef die-off are early candidates to tip. Already, Brazil’s Amazon rainforest has tipped from being a carbon sink to a carbon source. As Earth temperature rises to a new level (2oC to 4oC) several other tipping points become likely. Potentially the most devastating of those is the approaching collapse of the AMOC (Atlantic Meridional Overturning Circulation) which most of us mistakenly identify as the warm Gulf Stream but, in reality, plays much larger roles affecting European climate moderation, monsoons in Africa and Asia, Amazon forests, Antarctic ice melting and, generally, our ability to grow food crops.
There is hope! Tim Lenton, leading scientist on Tipping Points, has identified a variety of Positive Tipping Points in human behaviour that can propel rapid decarbonisation. Electrification of personal and commercial transport is one example. Likewise, is the increasing renewable energy generation, interest and adoption of circular economy principles, numerous projects around the world to change land use practices from carbon sources to carbon sinks. We have a long way to go, but consider one critical positive tipping point yet to be achieved: that humans, especially the relatively wealthy ones, start acting in concert as though the future well-being of our children rather than maintaining the material comforts of our lifestyles were our main priority.
