emperatures have risen by about 1 degree Celcius, or 1.8 degrees Fahrenheit, since pre-industrial times. Arctic summer sea ice extent has declined by around 40% since records began in 1979. Sea levels have been rising by about 3/32 inches a year since the early 1990s. Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. So yes: We are more confident than ever that humans have been the “dominant cause” of the rise in temperatures since the 1950s.
Although we often talk about uncertainty in future climate projections, there are some things we can be certain about. We know that Earth will continue to warm; we know that the adverse impacts of climate change are disproportionately larger as we go to higher temperatures and that the risk of irreversible and disastrous changes increases; we know that sea levels will continue to rise long after we have stabilized the Earth’s surface temperature and that melting of ice caps and glaciers will continue.
We also know that there will definitely be some level of climate change, no matter what happens with future carbon emissions, because of the existing accumulation of carbon within the atmosphere. This means that some level of adaptation will be necessary whatever we do. The scale of the potential investments, for example in flood and coastal defenses, the risks associated with failure, and the long lifetimes and lead times of such infrastructure together mean that future investments are likely to be highly sensitive to how the climate changes over the next two to three decades. We need to plan now for how we can climate-proof our lives, towns, and cities, and help to protect the natural environment, as there is virtually nothing in the climate system that seems likely to dampen the effects of our greenhouse gas emissions. Instead, the more we know, the more we are faced with the uncomfortable reality that this could be even more challenging than we previously thought.
In 2015, the Earth’s surface temperature passed the 1 degree Celcius (1.8 degrees Fahrenheit) threshold — halfway to the 2 degrees Celcius (3.6 degrees Fahrenheit) limit set in Paris — and yet we have already used two-thirds of the allowable budget of carbon that we can emit if we want to stay within that 2 degrees Celcius limit. Since then, new scientific evidence has indicated that this is an optimistic budget; the effects of melting permafrost and limitations on the ability of the biosphere to take up some of our carbon emissions suggest that we have even less room to maneuver than we thought.
Our climate in 2050
The year 2050 is not that far away in terms of climate timescales, and we can paint a picture of what the world’s future climate might be like with some degree of certainty. I won’t go into an exhaustive list of facts and figures, but will try to draw out some of the human consequences of what our world might be like if we don’t manage to reduce our emissions substantially. For instance, we know that the worst impacts will be felt by the world’s poorest, who are already under enormous stress and have very few resources at hand to help them survive.
So let us fast forward to 2050. The Earth’s surface temperature has passed 2 degrees Celcius (3.6 degrees Fahrenheit) above what it was just a century earlier, and in the same period, the global sea level has risen by another foot. The Arctic is now ice-free in summer, and there have been substantial increases in its ocean temperatures. Marine mammal, fish, and bird populations are changing, and the indigenous population is increasingly compromised by lack of food security; loss of coastal sea ice, sea level rise, and increased weather intensity are forcing relocation of some communities. The opening up of the Arctic has made it a major shipping route for international trade, and exploitation of the Arctic’s natural resources is growing rapidly. New invasive species, brought in by increased human activity, are changing the natural ecosystems.
In India, pre-monsoon heat is now crippling for much of the population, especially across the northern plains, and flooding during the monsoon season is increasingly serious as daily rainfall intensities rise. Those living in low-lying coastal areas are experiencing more and more frequent incursions of seawater during storm surges as sea levels rise. Fresh water supplies are contaminated, agricultural land is damaged, and waterborne diseases are increasingly common. Forced migration is increasingly an issue. On the positive side, though, air quality has improved substantially and fewer people are affected by respiratory ailments.
Across the Tropics, construction and maintenance of infrastructure in major towns and cities have become more difficult as daytime temperatures frequently exceed thresholds where it is safe to work outside. Electricity demand for air conditioning is putting greater and greater pressure on supplies.
Several small island states, such as Kiribati in the central Pacific Ocean, are no longer habitable because of sea level rise, with the population now stateless and with an uncertain future; in others, coral bleaching has led to the loss of sustainable fisheries on which the population depends for their food security. Tourism, which was a major part of their economies, has fallen away.
Southern Australia and the Mediterranean, including the Middle East, are now in the grip of prolonged droughts and periods of extreme summer heat. Wildfires are becoming increasingly dangerous, threatening homes and urban environments and damaging natural ecosystems. Water security is becoming more and more of an issue as aquifers are depleted. In the United States, the weather is increasingly volatile with more extremes of temperature and rainfall. Summer heat waves are becoming more prevalent — eight of the 10 warmest years ever recorded in the U.S. have occurred in the last 20 years.
This small glimpse into what the climate of 2050 might be like is a stark reminder of why climate change will be such a determinant of our social and economic future, and of our role as custodians of the rich diversity of Earth’s natural ecosystems. In all of this, it is likely that water will become the most precious commodity on the planet. Understanding how regional rainfall patterns will change, the impacts of those on water availability and water quality, and the legal arguments of who owns water when rivers and aquifers cross national boundaries will be defining issues in the coming decades.
So far, debates on climate change have been dominated largely by uncertainty in the projections and the economic implications of dealing with the problem. But increasingly, climate change will become a moral issue. It is clear that the worst impacts will be felt by the world’s poorest, and that climate change has the potential to derail their socioeconomic development. As the UN Deputy High Commissioner for Human Rights Flavia Pansieri noted in 2015: “Human-induced climate change is not only an assault on the ecosystem that we share. It also undercuts the rights to health, to food, to water and sanitation, to adequate housing, and — for the people of small island states and coastal communities — even the right to self-determination.” Looking forward, the protection of basic human rights and the role of the developed world in supporting the developing world are likely to alter fundamentally the debate on how we deal with climate change.
There is no doubt that climate change will affect us all profoundly in the future, but it’s worth remembering that we do not forward blindly without any sense of what we may be facing. The construction of computer models that simulate the Earth’s climate and enable us to predict, from fundamental physical principles, how the weather and climate will evolve is one of the great scientific achievements of the last 50 years. In few other areas of science are we able to look to the future with the level of confidence that we now have in our climate predictions.
It is worth reflecting on the words of Vice-Admiral Robert Fitzroy, captain of the Beagle, who took Charles Darwin on his momentous voyages, but who was also the founder of the U.K. Met Office and who issued the first public weather forecasts. After the loss of the Royal Charter in a terrible storm in 1859, he wrote to The Times: “Man cannot still the raging of the wind, but he can predict it. He cannot appease the storm, but he can escape its violence, and if all the appliances available for the salvation of life [from shipwreck] were but properly employed the effects of these awful visitations might be wonderfully mitigated.”
Over 150 years ago, Fitzroy embarked on the long journey of making forecasts as a means of reducing and managing the impacts of severe weather, and these now also apply to how we will manage climate change. From the global to the local and from hours to decades, our understanding of weather and climate and the predictions we make enable us to plan for the future and serve to keep us safe. Let’s leave the final word, though, to the British-born astronaut and climate scientist Piers Sellers, who died of pancreatic cancer in December 2016. On receiving his diagnosis a year earlier he wrote a moving piece in the New York Times on his perspectives on climate change:
“New technologies have a way of bettering our lives in ways we cannot anticipate. There is no convincing, demonstrated reason to believe that our evolving future will be worse than our present, assuming careful management of the challenges and risks. History is replete with examples of us humans getting out of tight spots. The winners tended to be realistic, pragmatic, and flexible; the losers were often in denial of the threat… As an astronaut, I spacewalked 220 miles above the Earth. Floating alongside the International Space Station, I watched hurricanes cartwheel across oceans, the Amazon snake its way to the sea through a brilliant green carpet of forest, and gigantic nighttime thunderstorms flash and flare for hundreds of miles along the Equator. From this God’s-eye view, I saw how fragile and infinitely precious the Earth is. I’m hopeful for its future.”
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