Prepare for the New Abnormal

abnormal.png

Prepare for the “new abnormal”. That was what California Governor Jerry Brown told reporters last month, commenting on the deadly wildfires that have plagued the state this year. He’s right. California’s latest crisis builds on years of record-breaking droughts and heatwaves. The rest of the world, too, has had more than its fair share of extreme weather in 2018. The Lancet Countdown on health and climate change announced last week that 157 million more people were exposed to heatwave events in 2017, compared with 2000.

Such environmental disasters will only intensify. Governments, rightly, want to know what to do. Yet the climate-science community is struggling to offer useful answers.

In October, the Intergovernmental Panel on Climate Change (IPCC) released a report setting out why we must stop global warming at 1.5 °C above pre-industrial levels, and how to do so. It is grim reading. If the planet warms by 2 °C — the widely touted temperature limit in the 2015 Paris climate agreement — twice as many people will face water scarcity than if warming is limited to 1.5 °C. That extra warming will also expose more than 1.5 billion people to deadly heat extremes, and hundreds of millions of individuals to vector-borne diseases such as malaria, among other harms.

Planet much more sensitive to fossil-fuel emissions than past studies have shown, scientists say

But the latest IPCC special report underplays another alarming fact: global warming is accelerating. Three trends — rising emissions, declining air pollution and natural climate cycles — will combine over the next 20 years to make climate change faster and more furious than anticipated. In our view, there’s a good chance that we could breach the 1.5 °C level by 2030, not by 2040 as projected in the special report (see ‘Accelerated warming’). The climate-modelling community has not grappled enough with the rapid changes that policymakers care most about, preferring to focus on longer-term trends and equilibria.

Evidences

Three lines of evidence suggest that global warming will be faster than projected in the recent IPCC special report.

1.

Greenhouse-gas emissions are still rising. In 2017, industrial carbon dioxide emissions are estimated to have reached about 37 gigatonnes. This puts them on track with the highest emissions trajectory the IPCC has modelled so far. This dark news means that the next 25 years are poised to warm at a rate of 0.25–0.32 °C per decade. That is faster than the 0.2 °C per decade that we have experienced since the 2000s, and which the IPCC used in its special report.

2.

Governments are cleaning up air pollution faster than the IPCC and most climate modellers have assumed. For example, China reduced sulfur dioxide emissions from its power plants by 7–14% between 2014 and 2016. Mainstream climate models had expected them to rise. Lower pollution is better for crops and public health. But aerosols, including sulfates, nitrates and organic compounds, reflect sunlight. This shield of aerosols has kept the planet cooler, possibly by as much as 0.7 °C globally.

3.

There are signs that the planet might be entering a natural warm phase that could last for a couple of decades. The Pacific Ocean seems to be warming up, in accord with a slow climate cycle known as the Interdecadal Pacific Oscillation. This cycle modulates temperatures over the equatorial Pacific and over North America. Similarly, the mixing of deep and surface waters in the Atlantic Ocean (the Atlantic meridional overturning circulation) looks to have weakened since 2004, on the basis of data from drifting floats that probe the deep ocean. Without this mixing, more heat will stay in the atmosphere rather than going into the deep oceans, as it has in the past.

Four Approaches for a solution

Assess science in the near term. Policymakers should ask the IPCC for another special report, this time on the rates of climate change over the next 25 years. The panel should also look beyond the physical science itself and assess the speed at which political systems can respond, taking into account pressures to maintain the status quo from interest groups and bureaucrats. Researchers should improve climate models to describe the next 25 years in more detail, including the latest data on the state of the oceans and atmosphere, as well as natural cycles. They should do more to quantify the odds and impacts of extreme events. The evidence will be hard to muster, but it will be more useful in assessing real climate dangers and responses.

Rethink policy goals. Warming limits, such as the 1.5 °C goal, should be recognized as broad planning tools. Too often they are misconstrued as physical thresholds around which to design policies. The excessive reliance on ‘negative emissions technologies’ (that take up CO2) in the IPCC special report shows that it becomes harder to envision realistic policies the closer the world gets to such limits. It’s easy to bend models on paper, but much harder to implement real policies that work.

Design strategies for adaptation. The time for rapid adaptation has arrived. Policymakers need two types of information from scientists to guide their responses. First, they need to know what the potential local impacts will be at the scales of counties to cities. Some of this information could be gleaned by combining fine-resolution climate impact assessments with artificial intelligence for ‘big data’ analyses of weather extremes, health, property damage and other variables. Second, policymakers need to understand uncertainties in the ranges of probable climate impacts and responses. Even regions that are proactive in setting adaptation policies, such as California, lack information about the ever-changing risks of extreme warming, fires and rising seas. Research must be integrated across fields and stakeholders — urban planners, public-health management, agriculture and ecosystem services. Adaptation strategies should be adjustable if impacts unfold differently. More planning and costing is needed around the worst-case outcomes.

Understand options for rapid response. Climate assessments must evaluate quick ways of lessening climate impacts, such as through reducing emissions of methane, soot (or black carbon) and HFCs. Per tonne, these three ‘super pollutants’ have 25 to thousands of times the impact of CO2. Their atmospheric lifetimes are short — in the range of weeks (for soot) to about a decade (for methane and HFCs). Slashing these pollutants would potentially halve the warming trend over the next 25 years.

Sources: Nature link - Indipendent link