NP
Nonlinear Processes in Geosciences

Archives / 2019 / September

Abrupt Warming could bring our planet a “Hothouse Earth” with catastrophic consequences for our economy and society

Abrupt Warming could bring our planet a “Hothouse Earth” with catastrophic consequences for our economy and society

Most of us have enjoyed swings in childhood. Some have even tried to swing faster and make a full 360 degrees’ loop. Those who succeeded had a very strange feeling of not being able to predict whether, increasing the energy of the swing, the transition from normal oscillations and 360 loops would happen. Indeed, there is an energy threshold such that the swing goes from oscillations to full loops and the change in the behavior is abrupt. Say now that the swing is our planet and the energy pumped in the Earth system are the anthropogenic emissions, in a recently published paper in the Proceedings of the National Academy of Sciences (https://doi.org/10.1073/pnas.1810141115) Will Steffen and co-authors found that increasing the emissions would push the earth towards an abrupt change in trajectory, leading in a very short time span to a 5 degrees’ warmer climate.

Up to now, scientists have predicted a fast but smooth increase of the planet temperature with increasing anthropogenic emissions. Although catastrophic, this scenario would leave enough time to adapt our society to a warmer climate and the associated consequences such as sea-level rise. This study has however identified a series of interconnected factors which could cause a chain reaction and push the Earth towards a “hothouse” state. Deforestation, permafrost thawing, relative weakening of land and ocean physiological CO2 sinks can drive further warming – even if we stop emitting greenhouse gases. Like going through the full loop could cause injuries, this process is likely to be unstoppable and irreversible and will lead to devastating consequences. The authors say: “a Hothouse Earth trajectory will likely exceed the limits of adaptation and result in a substantial overall decrease in agricultural production, increased prices, and even more disparity between wealthy and poor countries”. A Hothouse Earth trajectory would almost certainly flood deltaic environments, increase the risk of damage from coastal storms, and eliminate coral reefs (and all of the benefits that they provide for societies) by the end of this century or earlier.

The results of this study have animated a debate in the climate change community and there is actually a substantial disagreement about the possibility of crossing the tipping point described in the article. The non-linear geophysics community is working hard to understand these critical phenomena in simple systems which represents idealized climate.

Workshop report: Mathematics of the Economy and Climate

Workshop report: Mathematics of the Economy and Climate

Just before the summer a group of about 40 scientists gathered in an old Monastery in the Netherlands (Kontakt der Kontinenten, Soesterberg) for a rather special collaborative workshop entitled “Mathematics of the economy and climate”. Mathematicians, climate scientists and economists – a group of scientists that normally does not mix and are rather unfamiliar with each other’s research – joined together for three days to learn from each other and discuss the most pressing research questions around ongoing climate change and its connections with the development of economic systems (http://mathplanetearth.nl/econclim.html).

The workshop included high-profile speakers from Imperial College, ENS Lyon, London School of Economics and Yale. Prof. Tony Smith from Yale reported on recent research using the integrated assessment model developed by his colleague William Nordhaus (Nobel prize 2018) and presented attempts to view the global economic system and its interaction with climate in a spatially resolved way. This and many other interesting talks triggered lively discussions on, e.g., the adequacy of models in general and in particular in the different fields of research. Uncertainty in both the climate response and the economic development was one issue that was extensively discussed as it appears that economists tend to assume future climate (measured by, e.g., the equilibrium or transient climate sensitivity) as relatively well-known and vice versa.

There is still a long way to go for a good understanding of the combined evolution and interaction of the climate and the economic system. This workshop was a starting point for the different disciplines to learn to talk to each other. Participants enjoyed discussing with academics from different areas in an open-minded atmosphere. Finally it became clear that there are exciting and novel mathematical techniques available such as numerical methods for stochastic differential equations and dynamical systems to tackle the challenges ahead.