Today we’d like to talk about tipping points and why they matter. First of all, we’re not referring to the ITV quiz show of the same name hosted by the disconcertingly ever young Ben Shepherd. (Although that’s not to say a full length piece couldn’t be written on his age defying stratagems, it’s just this isn’t that blog). No, what we’re talking about are climate related tipping points, the moment when we cross a threshold and a certain changes becomes effectively irreversible. Yes, that’s right, it’s time for another science-y blog…
Tipping points have been a known risk for quite a while, but they have received less press than some parts of the climate crisis because they are harder to predict. As a result, some scientists have felt that their potential impact has been understated in scientific models of future scenarios because it was easier to leave them out than grapple with the uncertainty they introduce.
However, both the understanding of individual tipping points and the computing power behind modelling are ever improving and so our understanding of the risks posed by the possible events is becoming ever clearer, and this may not surprise you dear reader, but the news is not great.
The two most commonly talked about tipping points involve the Amazon Rainforest and Antarctic ice shelves.
Falling Forest
The risk in the Amazon is increasingly occupying the minds of those far cleverer than this humble blog. The science suggests that at a certain point of depletion rainforests lose the ability to maintain their own ecosystems and enter terminal decline resulting in a permanent transition to a savannah style landscape. Put simply, not enough trees means not enough rain generation which in turn means even less tree growth and so on in a deathly cycle until there’s not a great deal left.
It is thought that already more than a third of the Amazon rainforest may already be in a condition where it could be expected to exist as open savannah rather than under tree cover. The actual tipping point depends on the level of climate change that accompanies deforestation. We know that over the last five years Brazilian President and all round right wing bad guy, Jair Bolsonaro, has been acquiescing in a massive increase in rainforest clearances following a decade of real progress in protecting the habitat under previous administrations.
According to the leading Amazon scientist, Carlos Nobre, if the climate conditions remained as they are today then a 40% deforestation of the Amazon would lead to a tipping point which could see 60-70% of the forest area turn into dry savannah.
He goes on to say:
“Then we look at what climate change might do. We concluded that if the temperature in the Amazon increases up to 4 degrees Celsius (7 degrees Fahrenheit), this will mean a hydrological cycle change with less rain and a longer dry season. It’s the same mechanism — savannization. So if you put all the perspectives together — deforestation, global warming, increased vulnerability to forest fires — we conclude that with the current rate of global warming, if we exceed 20 to 25 percent deforestation, then we reach the tipping point and 50 to 60 percent of the Amazon forest would become a savanna. That’s why we are making this warning — today we already have 15 to 17 percent total deforestation in the Amazon. So at the current rates of deforestation, we are 20 to 30 years off from reaching this tipping point.”
Now, this is a worse case scenario but it is not unfeasible. Current climate policies would see us on track for a potential three degree rise in average global temperatures but that doesn’t take into account local variations. Carlos Nobre’s vision may come to pass if we fail to heed the warning.
Tumbling Ice
In the depths of the Antarctic the size of challenge is similar. The risk lies in huge ice shelves falling into the ocean and driving up sea levels which in turn would threaten coastal cities with catastrophic flooding all over the globe.
The main area of focus is the Pine Island Glacier (and, in turn, the neighbouring Thwaites glacier) in West Antarctica. This giant, frozen lump is two thirds the size of the whole UK and is melting faster than any other in the region. Studies from March of this year confirmed and quantified for the first time the definitive existence of dangerous tipping points. Scientists fear that these large sheets of ice could enter a meltdown loop that could potentially raise sea levels by as much as three metres. Such a rise could displace millions of people in low lying areas and wipe whole Pacific islands from the map permanently.
The science of this is all incredibly complicated but the latest study by the University of Northumbria shows that; “For Pine Island Glacier… the glacier has at least three distinct tipping points. The third and final event, triggered by ocean temperatures increasing by 1.2C, leads to an irreversible retreat of the entire glacier.” To put that into perspective, since 1980 global sea temperatures have been rising by 0.18⁰C per decade. Taking into account existing temperature rises, we may have as little as 40 years until the last of those three irreversible tipping points is passed for the Pine Island glacier.
As we said earlier, it’s not great.
Come in Number Nine
The science of tipping points in general has been driven forward by the work of Swedish scientist Johan Rockstrὂm. In 2009 he helped lead the work which came up with a unified model for viewing the tipping points facing the planet. His system consists of nine planetary boundaries which are then graded green, yellow or red depending on how close they are to reaching their outer boundary or tipping point.
The diagram above shows the nine categories and how we’re currently doing on each. As you can see, we’ve already reached deep into the red on two out of nine. These are ‘Biogeochemical flows’ and’ Biosphere Integrity’.
Biogeochemical flows is all about our use of nitrogen and phosphorus, two key parts of modern farming methods. The Stockholm Resilience Centre explains the impact this has;
“Human activities now convert more atmospheric nitrogen into reactive forms than all of the Earth's terrestrial processes combined. Much of this new reactive nitrogen is emitted to the atmosphere in various forms rather than taken up by crops. When it is rained out, it pollutes waterways and coastal zones or accumulates in the terrestrial biosphere. Similarly, a relatively small proportion of phosphorus fertilizers applied to food production systems is taken up by plants; much of the phosphorus mobilized by humans also ends up in aquatic systems. These can become oxygen-starved as bacteria consume the blooms of algae that grow in response to the high nutrient supply.”
Biosphere integrity refers to the tragic loss of biodiversity the planet has witness in recent decades which has been driven by human demand for food and land. So drastic have these changes been that The Millennium Ecosystem Assessment of 2005 concluded that damage to ecosystems caused by human activities were more rapid in the past 50 years than at any time in human history.
Beyond these red triggers, there are two yellow, two green and two we simply don’t know as we don’t have accurate ways of measuring the state of them.
The idea of this unified system is that is gives a wide ranging view of the state of the planet beyond merely focusing on the single measurement of planetary warming, as key as that is. If we are looking at long term sustainability then this is how we need to view our world. We need to restore balance to our fragile planet and the only way to do that is to balance our resource use, our habitat husbandry and our wider impact so that we find a way back out of the hole we’ve dug ourselves.
Tipped?
The question, of course, is can we still stop these tipping points from occurring? Can we stop the ice melt in Antarctica and the loss of the Amazon?
The good news is that we can. A combination of international pressure and good domestic policies by a government determined to do the right thing, dramatically slowed deforestation of the Amazon between 2004 and 2015. The only obstacle to resuming that positive change is the politics of one man. Brazil has an election due in the next couple of years. A change of leadership can get us back on track.
In the frozen south, better understanding of the way that giant ice shelves melt is equipping us with the knowledge to find ways to protect them. Combine that with effective measures to slow global temperature changes and the loss of country sized chunks of ice is not inevitable.
The nine planetary boundaries also give us hope. One of the segments; ‘Atmospheric Aerosol Loading’ shows what we can do when we put our mind to it. During the 1980’s it became clear that aerosols such as CFC’s were causing huge damage to the ozone layer. Effectively regulatory action and behaviour change by consumers combined to reverse that damaging trend and today that sits as one of only two green segments on the model. We did that and we can do it again.
One down, eight to go…