Date: 2024-08-16 Page is: DBtxt003.php txt00016691
Climate Crisis
Ramping up the dialog
Climate change ... Experts agree that global heating of 4C by 2100 is a real possibility. The effects of such a rise will be extreme and require a drastic shift in the way we live
Peter Burgess You Founder/CEO at TrueValueMetrics.org developing True Value Impact Accounting It is not so much radical measures as it is to do decent sensible things at the same scale that established legacy industries continue to do anti-social and anti-environmental activities.
Peter Burgess
Crosses topple in the cemetery at Quinhagak in the Yukon delta, Alaska. Permafrost in the region is thawing. Photograph: Mark Ralston/AFP/Getty Images
Drowned cities; stagnant seas; intolerable heatwaves; entire nations uninhabitable… and more than 11 billion humans. A four-degree-warmer world is the stuff of nightmares and yet that’s where we’re heading in just decades.
While governments mull various carbon targets aimed at keeping human-induced global heating within safe levels – including new ambitions to reach net-zero emissions by 2050 – it’s worth looking ahead pragmatically at what happens if we fail. After all, many scientists think it’s highly unlikely that we will stay below 2C (above pre-industrial levels) by the end of the century, let alone 1.5C. Most countries are not making anywhere near enough progress to meet these internationally agreed targets.
Climate models predict we’re currently on track for a heating of somewhere between 3C and 4C for 2100, although bear in mind that these are global average temperatures – at the poles and over land (where people live), the increase may be double that. Predictions are tricky, however, as temperatures depend on how sensitive the climate is to carbon dioxide (CO2). Most models assume that it is not very sensitive – that’s where the lower 3C comes from – but a whole new set of models to be published in 2021 finds much greater sensitivity. They put heating at around 5C by the end of the century, meaning people could be experiencing as much as 10C of heating over land.
Such uncertainty isn’t ideal, but for our purposes let’s plump for an entirely feasible planetary heating of 4C by the end of the century. If that seems a long time away, consider that plenty of people you know will be around then. My children will be in their 80s, perhaps with middle-aged children and grandchildren. We are making their world and it will be a very different place.
Four degrees may not sound like much – after all, it is less than a typical temperature change between night and day. It might even sound pleasant, like retiring from the UK to southern Spain. However, an average heating of the entire globe by 4C would render the planet unrecognisable from anything humans have ever experienced. The last time the world was this hot was 15m years ago during the miocene, when intense volcanic eruptions in western North America emitted vast quantities of CO2. Sea levels rose some 40 metres higher than today and lush forests grew in Antarctica and the Arctic. However, that global heating took place over many thousands of years. Even at its most rapid, the rise in CO2 emissions occurred at a rate 1,000 times slower than ours has since the start of the Industrial Revolution. That gave animals and plants time to adapt to new conditions and, crucially, ecosystems had not been degraded by humans.
 over slower-growing trees, Betts says. To the south and north of this humid zone, bands of expansive desert will also rule out agriculture and human habitation. Some models predict that desert conditions will stretch from the Sahara right up through south and central Europe, drying rivers including the Danube and the Rhine.
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Our best hope lies in cooperating as never before: decoupling the political map from geography
In South America, the picture is more complicated: increased precipitation could enhance the Amazon rainforest, leading to mightier river flow. Other models predict a weakening of the easterlies over the Atlantic, drying the Amazon, increasing fires and turning it from forest to grassland. The tipping point for the Amazon could well be triggered by deforestation; while the intact forest could cope with some drought because it generates and maintains its own moist ecosystem, areas that have been opened up through degradation allow moisture to escape. “A combination of climate change and deforestation could push it into a savannah state,” Rockström says.
All of nature will be affected by the change in climate, ecosystems and hydrology and there will be plenty of extinctions as species struggle to migrate and adapt to an utterly changed world. Daniel Rothman, co-director of MIT’s Lorenz Center, calculates that 2100 will herald the beginning of Earth’s sixth mass extinction event. But what about us? This is undoubtedly a more hostile, dangerous world for humanity, which by 2100 will number around 11 billion, all of whom will need food, water, power and somewhere to live. It will be, in a giant understatement, problematic.
The good news is that humans won’t become extinct – the species can survive with just a few hundred individuals; the bad news is, we risk great loss of life and perhaps the end of our civilisations. Many of the places where people live and grow food will no longer be suitable for either. Higher sea levels will make today’s low-lying islands and many coastal regions, where nearly half the global population live, uninhabitable, generating an estimated 2 billion refugees by 2100. Bangladesh alone will lose one-third of its land area, including its main breadbasket.
From 2030, more than half the population will live in the tropics, an area that makes up a third of the planet and already struggles with climate impacts. Yet by 2100, most of the low and mid latitudes will be uninhabitable because of heat stress or drought; despite stronger precipitation, the hotter soils will lead to faster evaporation and most populations will struggle for fresh water. We will have to live on a smaller land surface with a larger population.
Indeed, the consequences of a 4C warmer world are so terrifying that most scientists would rather not contemplate them, let alone work out a survival strategy.
Rockström doesn’t like our chances. “It’s difficult to see how we could accommodate a billion people or even half of that,” he says. “There will be a rich minority of people who survive with modern lifestyles, no doubt, but it will be a turbulent, conflict-ridden world.”