‘Given that it remains uncertain whether adaptation and further progress toward development goals will be possible at this level of climate change, the projected 4°C warming simply must not be allowed to occur’ World Bank report
WHO: The Potsdam Institute for Climate Impact Research and Climate Analytics, commissioned by the World Bank
WHAT: A report looking at the impacts of 4oC of global warming and the risk to human systems
WHEN: November 2012
WHERE: The World Bank’s website
TITLE: Turn down the heat: Why a 4oC warmer world must be avoided
This is part two; part one is here.
What does a 4oC world look like?
It looks like a place where climate change has undermined economic growth through natural disaster after natural disaster which eventually overwhelms emergency response capabilities.
It looks like a world where all of the gains towards to the Millennium Development Goals of eradicating poverty and hunger have been wiped out by the negative impacts of climate change, and extreme heat stress has caused a 60% or more reduction in crop yield.
It looks like a world where even wealthy industrialised countries are no longer able to adapt to or meet development goals because of climate change and where entire coastal cities have been abandoned because the cost of fortifying them against rising sea levels was too great.
How could this happen? How could the change from 2oC to 4oC be the difference between continuing economic growth in a green economy and abandoned flooded cities?
Non-linear and cascading impacts.
Cast your minds back with me to high school math where you learned about exponential graphs. The ones that were y=x2 and you had to solve for x in your exams and it hurt your brain? This is non-linear and what is likely to happen with the planet. Take the oceans for example. While we still have sea ice in the Arctic, the warming from the oceans sucking up almost half of our carbon emissions every year is still relatively slow. However, once the ice melts and it’s all open water for the first time, that’s when warming gets going and it will likely ramp up like an exponential graph.
In fact, if you really feel like nerding it up, you can simulate sea ice at home and watch the tipping point happen. Put ice and water into a pot and once it’s cold (1-2oC) turn the heat on high and take the temperature every 30 seconds until the ice is all gone and the water is getting hotter (15-20oC or longer if you want). Graph the results and find your tipping point. Science!
The final chapter in the World Bank report looks at the potential implications for a 4oC world in terms of risk management. If it’s going to cost a certain number of trillion dollars to prepare for 2oC, should we just double the amount and prepare for 4oC? They think that may not be enough since ‘lurking in the tails of the probability distributions are likely to be many unpleasant surprises’.
The report points out that since cascading effects are very difficult to predict, that most of the predictions I covered in part one are based on linear models and likely to be conservative estimates of what will happen with 4oC warming. They are also sector based and don’t take into account what happens when impacts team up and work together.
Going back to the oceans again, what will the cumulative impacts be of all the effects that have been studied separately? What happens when coral reefs collapse, marine production reduces from rising temperatures and acidification, low-lying coastal areas are inundated from sea level rise, and human economic and social impacts are all lumped together at the same time?
The report states that there is a high level of concern that all of those effects all happening together at once hasn’t really been studied or quantified beyond ‘horrifying’.
From what we know now from all of the leading research, this is a list of potential tipping points from the report:
This may be the coral reef tipping point which will create larger storm surges for coastal areas that were previously protected. It also means an economically significant loss of tourism dollars for places like the Great Barrier Reef.
This could also be the tipping point for the Greenland Ice Sheet which has been melting faster than expected (was previously predicted for 4.6oC). There is approximately 6-7m of sea level rise in this ice sheet, so New York City may need to move inland.
This could be the tipping point for the Amazon Rainforest, where large parts of the rainforest die off from lack of water and release more carbon into the atmosphere, further fuelling climate change in a positive feedback loop that it will be almost impossible to recover from.
This could also be the point for the West Antarctic Ice Sheet which has 3m of additional sea level rise stored in it. New York City will need to keep moving.
This is the probable tipping point for world agriculture as crops start dying from heat stress. The IPCC assessment predicts that crop yields will decrease between 63-82%. Keep in mind that this goes hand in hand with a population increase to 9 billion people.
This is also the point at which the accumulated stresses from 2oC and 3oC overwhelms emergency and health services and all of the gains made to alleviate poverty are also overwhelmed by the negative consequences from climate change.
Once the World Bank has laid out for us exactly how horrible it could possibly get in a way we can’t easily predict, plan for, adapt to safely or afford, this is the very simple conclusion they have that we should all be able to agree with:
‘Given that it remains uncertain whether adaptation and further progress toward development goals will be possible at this level of climate change, the projected 4°C warming simply must not be allowed to occur—the heat must be turned down. Only early, cooperative, international actions can make that happen.’