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12 November, 2019 00:00 00 AM

Climate change is not just about temperature

Lots of small changes will help inspire larger-scale shifts in policy and economic frameworks
Mohammed Abul Kalam, PhD
Climate change is not just 
about temperature

What if the nightly news had regular updates on forest clearing, ocean temperatures, and fossil fuel consumption? These indicators sit alongside temperatures as signs of climate change. Exactly 40 years ago, a small group of scientists met at the world’s first climate conference in Geneva. They raised the alarm about unnerving climate trends. Today, more than 11,000 scientists have co-signed a letter in the Journal of Bioscience, calling for urgently necessary action on climate. This is the largest number of scientists to explicitly support a publication calling for climate action. They come from many different fields, reflecting the harm our changing climate is doing to every part of the natural world.

This month the world has been celebrating the 50th anniversary of Neil Armstrong setting foot on the moon. But this week sees another scientific anniversary, perhaps just as important for the future of civilization. Forty years ago, a group of climate scientists sat down at Woods Hole in Massachusetts for the first meeting of the “Ad Hoc Group on Carbon Dioxide and Climate”. It led to the preparation of what became known as the Charney Report – the first comprehensive assessment of global climate change due to carbon dioxide.

It doesn’t sound as impressive as landing on the moon, and they're certainly weren’t millions waiting with bated breath for the deliberations of the meeting. But the Charney Report is an exemplar of good science, and the success of its predictions over the past 40 years has firmly established the science of global warming.

What is this ‘greenhouse gas’ we speak of? Other scientists, starting in the 19th century, had already demonstrated that carbon dioxide was what we now call a “greenhouse gas”. By the 1950s, scientists were predicting warming of several degrees from the burning of fossil fuels. In 1972 John Sawyer, the head of research at the UK Meteorological Office, wrote a four-page paper published in Nature summarizing what was known at the time and predicting warming of about 0.6℃ by the end of the 20th century.

But these predictions were still controversial in the 1970s. The world had, if anything, cooled since the middle of the 20th century, and there was even some speculation in the media that perhaps we were headed for an ice age.  The meeting at Woods Hole gathered together about 10 distinguished climate scientists, who also sought advice from other scientists from across the world. The group was led by Jule Charney from the Massachusetts Institute of Technology, one of the most respected atmospheric scientists of the 20th century.

The Report lays out clearly what was known about the likely effects of increasing carbon dioxide on the climate, as well as the uncertainties. The main conclusion of the Report was direct: We estimate the most probable warming for a doubling of CO₂ to be near 3℃ with a probable error of 1.5℃.

In the 40 years since their meeting, the annual average CO₂ concentration in the atmosphere, as measured at Mauna Loa in Hawaii, has increased by about 21%. Over the same period, global average surface temperature has increased by about 0.66℃, almost exactly what could have been expected if a doubling of CO₂ produces about 2.5℃ warming – just a bit below their best estimate– a remarkably prescient prediction.

The Charney Report’s authors didn’t just uncritically summarize the science. They also acted skeptically, trying to find factors that might invalidate their conclusions. They concluded: We have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warming’ due to a doubling of atmospheric CO₂ to negligible proportions or to reverse them altogether. The report and the successful verification of its prediction provide a firm scientific basis for the discussion of what we should do about global warming.

Over the ensuing 40 years, as the world warmed pretty much as Charney and his colleagues expected, climate change science improved, with better models that included some of the factors missing from their 1979 deliberations. This subsequent science has, however, only confirmed the conclusions of the Charney Report, although much more detailed predictions of climate change are now possible.

Why no change? If you’re thinking not much has changed in the past 40 years, you might be right. Globally, greenhouse gas emissions are still rising, with increasingly damaging effects. Much of the focus to date has been on tracking global surface temperatures. This makes sense, as goals like “prevent 2℃ of warming” create a relatively simple and easy-to-communicate message.

However, there’s more to climate change than global temperature. The indicators include human population growth, tree cover loss, fertility rates, fossil fuel subsidies, glacier thickness, and frequency of extreme weather events. All are linked to climate change.

Troubling signs over the past 40 years: Profoundly troubling signs linked to human activities include sustained increases in human and ruminant populations, global tree cover loss, fossil fuel consumption, number of plane passengers, and carbon dioxide emissions. The concurrent trends on the actual impacts of climate change are equally troubling. Sea ice is rapidly disappearing, and ocean heat, ocean acidity, sea level, and extreme weather events are all trending upwards. These trends need to be closely monitored to assess how we are responding to the climate emergency. Anyone of them could hit a point of no return, creating a catastrophic feedback loop that could make more regions of Earth uninhabitable.

The concept of a “tipping point” – a threshold beyond which a system shifts to a new state – is becoming a familiar one in discussions of the climate. Examples of tipping points are everywhere: a glass falling off a table upon tilting; a bacterial population hitting a level where it pushes your body into a fever; the boiling point of water, or a cube of ice being thrown into warm water, where it rapidly melts.

The ice cube is a poignant example because scientists now fear that West Antarctica’s ice sheets are also leading towards irreversible melting. Likewise, the recent discovery of deep canyons beneath the Greenland ice sheet raises concerns regarding its stability.

The history of the atmosphere, oceans, and ice caps indicate that, once changes in the energy level which drive either warming or cooling reach a critical threshold, irreversible tipping points ensue.

Over the threshold: An increase in global temperatures can lead to a threshold representing the culmination and synergy of multiple processes, such as release of methane from permafrost or polar ocean sediments, retreating sea ice and ice sheets, warming oceans, collapse of ocean current systems such as the North Atlantic Thermohaline Current and – not least – large scale fires.

The question is whether the post-18th-century global warming trend may culminate in a major tipping point or, alternatively, is represented by an increase in disparate extreme weather events, as are currently occurring around the world.

The question of tipping points is of critical importance since it affects future climate projections and adaptation plans. In this regard, the latest Intergovernmental Panel on Climate Change Report leaves the question of tipping points open.

Following the paper I could suggest six critical and interrelated steps that governments, and the rest of humanity, can take to lessen the worst effects of climate change: (1) prioritize energy efficiency, and replace fossil fuels with low-carbon renewable energy sources, (2) reduce emissions of short-lived pollutants like methane and soot, (3) protect and restore the Earth’s ecosystems by curbing land clearing, (4) reduce our meat consumption, (5) move away from unsustainable ideas of ever-increasing economic and resource consumption, and (6) stabilize and ideally, gradually reduce human populations while improving human well-being.

We recognise that many of these recommendations are not new. But mitigating and adapting to climate change will entail major transformations across all six areas. Lots of small changes will help inspire larger-scale shifts in policy and economic frameworks. We are encouraged by a recent global surge of concern. Some governments are declaring climate emergencies. Grassroots citizen movements are demanding change.  And as a medical sociologist, I urge widespread use of these indicators to track how changes across the six areas above will start to change our ecosystem trajectories. The writer is Former Head, Department of Medical Sociology, Institute of Epidemiology, Disease Control & Research (IEDCR),  Dhaka, Bangladesh



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Editor : M. Shamsur Rahman
Published by the Editor on behalf of Independent Publications Limited at Media Printers, 446/H, Tejgaon I/A, Dhaka-1215.
Editorial, News & Commercial Offices : Beximco Media Complex, 149-150 Tejgaon I/A, Dhaka-1208, Bangladesh. GPO Box No. 934, Dhaka-1000.

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