The Intergovernmental Panel on Climate Change (IPCC) warns humans are unequivocally warming the planet, and that is triggering rapid changes in the atmosphere, oceans, and polar regions, and increasing extreme weather around the world.
The IPCC's Sixth Assessment Report on Aug 9 drew on research from 234 scientists from around the globe. It looks at how the earth is changing as temperatures rise and points to the implications for the future. I was one of the scientists.
The facts about climate change have been clear for a long time, with the evidence just continuing to grow. The warning signs have been clear over the last decade, with each new emergency topping its precedent.
Global temperatures are rising, producing more droughts and wildfires, increasing the intensity of storms, causing catastrophic flooding, and raising sea levels.
Rising seas increase the vulnerability of cities and the infrastructure that line many coastlines around the world because of flooding, erosion, destruction of coastal ecosystems and contamination of surface and ground waters.
Mainland China, Bangladesh, India, Vietnam, Indonesia, and Thailand are home to the most people living on land projected to be below average annual coastal flood levels by 2050. Together, those six nations account for roughly 75 per cent of the 300 million people on land facing the same vulnerability at mid-century.
Global sea level is rising at a rate unmatched for at least thousands of years. The primary reason is that global temperatures are rising, causing ocean water to expand and land ice to melt. About a third of its current rise comes from thermal expansion - when water grows in volume as it warms. The rest comes from the melting of ice on land.
Antarctica is the existential threat to coastal nations. It is twice the size of Australia (more than 20,000 times the size of Singapore). Its ice sheet is 2km to 3km thick and has enough water to raise sea levels by 65m - that is more than the height of the Singapore ArtScience Museum and the Supertree of Gardens by the Bay. But we need only a few per cent of the Antarctic ice sheet to melt to have a devastating impact.
Ominously, satellite-based measurements of the Greenland and Antarctic ice sheets show that this melting is accelerating. Greenland is now the biggest contributor to global sea-level rise.
Greenland went from dumping only about 51 billion tonnes of ice into the ocean between 1980 and 1990, to losing 286 billion tonnes between 2010 and 2018. That is a staggering 76 trillion gallons of water added to the ocean each year, which is equivalent to 114 million Olympic-size swimming pools.
Sea-level rise through 2050 is fixed. No matter how quickly nations lower emissions now, the world is looking at about 15cm to 30cm of sea-level rise through the middle of the century, given the long-drawn impact of global warming on the oceans and ice sheets.
Even under a stable climate, sea-level rise is expected to continue slowly for centuries.
Beyond 2050, sea-level rise becomes increasingly susceptible to the world's emissions choices. If countries choose to continue their current paths, greenhouse gas emissions will likely result in 3 deg C to 4 deg C of warming by 2100, and a sea level rise of up to 1m.
Under the most extreme emissions scenario, rapid ice sheet loss from Greenland and Antarctica could lead to a sea level rise approaching 2m by the end of this century. At this point, inundation goes from being an existential threat to reality for many coastal nations. Singapore won't be spared its impact.
What these figures tell us is that adaptation to seal-level rise is a long-term obligation, which coastal policy and practice are only just beginning to recognise.
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What can we do
But there is hope to survive sea-level rise.
The IPCC report has shown a growing understanding of the causes of climate change and their solutions.
A 2 deg C warmer world, consistent with the Paris Agreement, would see lower sea-level rise, most likely about half a metre by 2100. What's more, the more the world limits its greenhouse gas emissions, the lower the chance of its triggering rapid ice sheet loss from Greenland and Antarctica.
But time is running out to meet the ambitious goal laid out in the Paris Agreement to limit warming to well below 2 deg C above pre-industrial levels.
We must hold our elected officials accountable to the promises they have made on climate change. Indeed, we may require reductions far more than those that have been pledged by nations in the run up to COP26, the United Nations climate summit to be held in Glasgow in November.
Fortunately, attitudes across the world towards climate change have shifted in the past decade. Where once there was ignorance, inattention, and disbelief about climate change, now there is concern.
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Individually, we can actively contribute to the fight to tackle the climate emergency. Volunteering and spreading awareness to other people about the effects of climate change, coupled with attempting to live a more sustainable life, can make all the difference.
Technological advances are also a cause for hope. Solar and wind energy and battery technology are now far cheaper, and their efficiency is getting better and better. New technologies, including artificial intelligence, now also offer the prospect of huge improvements in the energy efficiency of transport systems, building operations, manufacturing processes and food production.
The planet's oceans, forests and grasslands take up huge quantities of carbon dioxide through photosynthesis, much of which is stored in plants or in the soil, creating major global carbon sinks.
By preserving and expanding forests, these sinks could be made larger. Taking greater care of oceans and land is not only important for preserving biodiversity but is also a key part of climate change mitigation.
I believe that climate change is the one challenge that will define the contours of this century more dramatically than all others.
Surviving sea-level rise is going to change our lives; it is going to change the way we regard ourselves on the planet; if we rise to the challenge, it will lead to a happier, more equitable way of life for all of humankind.
Only then can we leave behind a world that is worthy of our children, where there is reduced conflict and greater cooperation - a world marked not by human suffering, but by human progress.
• Benjamin P. Horton is Director of the Earth Observatory of Singapore, Nanyang Technological University. He contributed this article to mark this year's World News Day.
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