The small change that makes a big difference in global warming
By KENNETH LIM
Let’s take a walk on the Celsius scale.
We’ll start at 1°C above pre-industrial levels. That is where the world is today, and it represents how far the global average temperature has risen since 1750. The world's surface has grown hotter in each of the last three decades than any earlier decade since 1850, according to research analysed by the Intergovernmental Panel on Climate Change (IPCC). Ocean surface temperatures have been rising by about 0.11°C per decade since 1971. The Arctic sea-ice has very likely been shrinking by 3.5 to 4.1 per cent per decade over the past 40 years. In other words, the Earth has a fever.Now go up half a degree, to 1.5°C over pre-industrial levels. That is the threshold below which signatories of the 2016 Paris Agreement are trying to keep global temperatures. It is an ambitious target, but also highly aspirational – countries only have to try, but do not have to meet it.The organisms featured in this article are all threatened or endangered. The loss of biodiversity is a growing concern as warming alters ecosystems.What actually happens when warming is capped at 1.5°C, and what if we overshoot by a little, is murky because research is sparse. For instance, whether the polar ice sheets can recover at this level, and how long they might need to do so, is still unknown. That lack of research exists not so much because 1.5°C is uninteresting, but more because few scientists had expected politicians to agree to such an aggressive target, and so they had not studied it closely in scenario analyses. The IPCC is looking to address that gap, however, with a report on 1.5°C slated for 2018.Still, we know that extreme weather will become more commonplace, according to a study led by research firm Climate Analytics. Temperatures that were seen only once every thousand days in pre-industrial times will be about 15 times more likely to occur at 1.5°C. Storms that were once seen only every thousand days will be 45 per cent more likely to form. About 90 per cent of coral reefs will be at risk of long-term damage from bleaching.Maize and wheat production will fall in tropical areas, although carbon dioxide-fuelled photosynthesis may increase yields of rice and soy. The science may not be comprehensive, but tropical areas already know that they will be more affected by the probable changes, and so 1.5°C remains an important target for countries in the tropics.
More is known when we go another half a degree higher, to 2°C above pre-industrial levels, enough for the Paris Agreement to draw a line and require signatory countries to keep the increase in global average temperatures “well below” this threshold. At 2°C, the probability of once-in-a-thousand-years temperatures are 27 times higher than in pre-industrial times.Virtually all – 98 per cent, to be precise – coral reefs will be at risk of long-term bleaching damage. A 2016 paper by US academics Solomon Hsiang and Adam Sobel showed that tropical populations of plants and animals would have to move more than 1,000 kilometres toward the poles in less than a century if global temperatures rise by 2°C over the same period.The concern is that if humans allow the world to warm more than 2°C above pre-industrial levels, the world’s climate might undergo irreversible change and reach a new equilibrium. As IPCC notes, “the precise levels of climate change sufficient to trigger abrupt and irreversible change remain uncertain, but the risk associated with crossing such thresholds increases with rising temperature”.That is what is at stake. With each half-degree of global warming from where the world stands today, the planet takes a step toward extreme climate change, and humans take a step away from being able to repair the damage.But there is now greater consensus than ever before about what needs to be done, and greater will to do it. 197 countries have agreed to the Paris pact. 143 of those, including Singapore, have ratified. That is no small feat. As part of the treaty, each country pledges through Nationally Determined Contributions (NDCs) to mitigate its own greenhouse gas emissions at a pace of its own choosing. Singapore’s NDC, for instance, aims to reduce business-as-usual emissions of greenhouse gases in 2020 by 16 per cent and to reduce greenhouse gas emissions intensity, or the amount of emissions per dollar of GDP, by 36 per cent of 2005 levels by 2030.To meet those targets, a sea change will have to sweep over the world. Consider that greenhouse gas emissions as a result of human activity was about 49 billion tonnes of carbon dioxide equivalent in 2010, give or take 4.5 billion tonnes, according to IPCC. To have a “likely” chance of keeping temperatures within a 2°C increase, the world must cut its annual emissions by 41 to 72 per cent from 2010 levels by 2050, or by 78 per cent to 118 per cent by 2100 (cutting by more than 100 per cent would require a net removal of greenhouse gases from the atmosphere), the report said. Imagine electric and hybrid cars becoming the norm and power grids that draw at least half of their energy from renewable sources.For Singapore, the implementation strategy includes studying renewable energy sources such as solar, which could alter the power generation landscape in the country. There will be less burning of plastics, but more incineration of sludge waste that would otherwise end up in landfills. Electrical goods will be more efficient as the government raises minimum energy performance standards and extends them to more products. After 2019, a carbon tax on power plants is expected to take effect.And yet, even if every country in the world were to follow through on its self-determined pledge, it would not be enough to keep warming within a 2°C increase, much less the loftier 1.5°C target.Climate Action Tracker, an independent research firm, analysed the potential impact of what countries say they will do and estimated that the pledges and promises of governments, including NDCs, as at Nov 1, 2016, would limit global warming to about 2.8°C above pre-industrial levels. And governments have to get around to actually carrying out those pledges; current policies alone are expected to limit warming to about 3.6°C above pre-industrial levels.Whether those pledges will actually be kept is a grand challenge of its own. Already, the United States, the world’s largest emitter of carbon dioxide, is wavering on its commitment to the treaty. The Green Climate Fund, through which developed countries have agreed to provide US$100 billion of green financing to developing countries, is beset with criticism about slow deployment of assets and grumblings that the amount of money pledged to date is far from the required amount. Intent and action do not always go hand in hand.
All is not lost. Climate Action Tracker, citing IPCC data, notes that it is still possible to stay within the 1.5°C and 2°C targets from the current starting point. But the key is to start early. Because it is the volume of greenhouse gases that determines the rate of warming, a slow start to cutting emissions will require more aggressive – and costlier – mitigation later on.In the politics and science of climate change, the innocuous half-degree looms large. That tiny increment, less than the distance between two marks on a thermometer, separates success and failure, hope and despair.It may be just half a degree, but it means a world of change.Web design: Yu Kexin