COP26 climate talks in Glasgow starting next Sunday may be the world’s best last chance to cap global warming at the 1.5-2 degrees Celsius upper limit set out in the 2015 Paris Agreement.

The stakes for the planet are huge – among them the impact on economic livelihoods the world over and the future stability of the global financial system.

Here are 10 climate change-related questions that economic policy-makers are trying to answer:

1) HOW MUCH DOES CLIMATE CHANGE COST? From floods and fires to conflict and migration: economic models struggle with the many possible knock-on effects from global warming. The ballpark IMF estimate is that unchecked warming would shave 7% off world output by 2100. The Network for Greening the Financial System (NFGS) group of world central banks puts it even higher – 13%. In a Reuters poll of economists, the median figure for the output loss in that scenario was 18%.

2) WHERE IS THE IMPACT GOING TO BE FELT HARDEST? – Clearly, the developing world. Much of the world’s poor live in the tropical or low-lying regions already suffering climate change fall-out like droughts or rising sea levels. Moreover their countries rarely have the resources to mitigate such damage. The NFGS report projects overall output losses of above 15% for much of Asia and Africa, rising to 20% in the Sahel countries.

3) WHAT DOES THAT MEAN FOR INDIVIDUAL LIVELIHOODS? Climate change will drive up to 132 million more people into extreme poverty by 2030, a World Bank paper last year concluded. Factors included lost farming income; lower outdoor labour productivity; rising food prices; increased disease; and economic losses from extreme weather.

4) HOW MUCH WILL IT COST TO FIX IT? Advocates of early action say the sooner you start the better. The widely used NiGEM macroeconomic forecast model even suggests an early start would offer small net gains for output thanks to the big investments needed in green infrastructure. The same model warns of output losses of up to 3% in last-minute transition scenarios.

5) WHO LOSES OUT IN A “NET ZERO” CARBON WORLD? Primarily, anyone with fossil fuel exposure. A report by think tank Carbon Tracker in September estimated that over $1 trillion of business-as-usual investment by the oil and gas sector would no longer be viable in a genuinely low-carbon world. Moreover the IMF has called for the end of all fossil fuel subsidies – which it calculates at $5 trillion annually if defined to include undercharging for supply, environmental and health costs.

6) WHAT SHOULD CARBON REALLY COST? Tax or permit schemes that try to price in the damage done by emissions create incentives to go green. But so far only a fifth of global carbon emissions are covered by such programmes, pricing carbon on average at a mere $3 a tonne. That’s well below the $75/tonne the IMF says is needed to cap global warming at well below 2°C. The Reuters poll of economists recommended $100/tonne.

7) WOULDN’T THAT LEAD TO INFLATION? – Anything which factors in the polluting cost of fossil fuels is likely to lead to price rises in some sectors – aviation for example. That could in turn lead to what central banks define as inflation – broad-based and durable price rises across the whole economy. Yet history shows this hasn’t necessarily been the case: carbon taxes introduced in Canada and Europe pushed overall prices lower because they cut into household income and hence consumer demand, a recent study showed. It is also true that doing nothing could lead to inflation: a European Central Bank paper last year warned of food and commodity price rises from extreme weather events and the land shortages being caused by desertification and rising sea levels.

8) ARE GREEN ADVANCES REALLY DECOUPLING EMISSIONS FROM ECONOMIC GROWTH? Genuinely sustainable growth implies that economic activity can grow as needed without adding yet more emissions. This is the holy grail of “absolute decoupling”. But so far, any decoupling has either been largely relative – in the sense of merely achieving higher rates of economic growth than gains in emissions – or achieved by shifting dirty production from one national territory to another. And that is why, for now, global emissions are still rising.

9) WHO BEARS THE BRUNT OF TRANSITION? The idea of “Just Transition” has been espoused by bodies such as the European Union to acknowledge that the transition to net zero should happen in a fair way – for example by ensuring low-income groups are not made worse-off. At a global scale, the rich countries which since their industrial revolutions have generated the bulk of emissions have promised to help developing countries transition via $100 billion of annual transfers – a promise so far not fulfilled.

10) COULD THIS SPARK A FINANCIAL CRISIS? The global financial system needs to be insulated against both the physical risks of climate change itself and the upheavals likely to happen during a transition to net zero. Central banks and national treasuries are calling on banks and other financial players to come clean about the exposure of their books to such risks. The ECB and other regulators have made it clear there is a long way to go on this.

(Editing by Giles Elgood)

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A region in Assam affected by floods in 2015. Photo: Pradip Nemane/Wikimedia Commons

• The climate of Earth has always changed, but the study of past climates shows us that the changes in the last 150 years have been exceptional and can’t be natural.
• Taking the whole range of climate models suggests a doubling of carbon dioxide could warm the planet by 2º to 4.5º C, with an average of 3.1º C.
• There is no scientific support for the continual denial of climate change.

The science of climate change is more than 150 years old and it is probably the most tested area of modern science. However the energy industry, political lobbyists and others have spent the last 30 years sowing doubt about the science where none really exists. The latest estimate is that the world’s five largest publicly-owned oil and gas companies spend about $200m each year on lobbying to control, delay or block binding climate-motivated policy.

This organised and orchestrated climate change science denial has contributed to the lack of progress in reducing global green house gas (GHG) emissions – to the point that we are facing a global climate emergency. And when climate change deniers use certain myths – at best fake news and at worse straight lies – to undermine the science of climate change, ordinary people can find it hard to see through the fog. Here are five commonly used myths and the real science that debunks them.

1. Climate change is just part of the natural cycle

The climate of Earth has always changed, but the study of palaeoclimatology, or past climates, shows us that the changes in the last 150 years – since the start of the industrial revolution – have been exceptional and cannot be natural. Modelling results suggest that future predicted warming could be unprecedented compared to the previous 5m years.

The “natural changes” argument is supplemented with the story that Earth’s climate is just recovering from the cooler temperatures of the Little Ice Age (1300-1850AD) and that temperatures today are really the same as the Medieval Warm Period (900-1300 AD). The problem is that both the Little Ice Age and the Medieval Warming period were not global but regional changes in climate affecting north-west Europe, eastern America, Greenland and Iceland.

Also read: The Himalaya Are Becoming Giant Cash Cows

A study using 700 climate records showed that, over the last 2,000 years, the only time the climate all around the world changed at the same time and in the same direction has been in the last 150 years, when over 98% of the surface of the planet has warmed.

2. Changes are due to sunspots/galactic cosmic rays

Sunspots are storms on the Sun’s surface that come with intense magnetic activity and can be accompanied by solar flares. These sunspots do have the power to modify the climate on Earth. But scientists using sensors on satellites have been recording the amount of the Sun’s energy hitting Earth since 1978 and there has been no upward trend. So they cannot be the cause of the recent global warming.

Galactic cosmic rays (GCRs) are high-energy radiation that originates outside our solar system and may even be from distant galaxies. It has been suggested that they may help to seed or “make” clouds. So reduced GCRs hitting the Earth would mean fewer clouds, which would reflect less sunlight back into space and so cause Earth to warm.

But there are two problems with this idea. First, the scientific evidence shows that GCRs are not very effective at seeding clouds. And second, over the last 50 years, the amount of GCRs have actually increased, hitting record levels in recent years. If this idea were correct, GCRs should be cooling Earth, which they aren’t.

3. CO₂ is a small part of the atmosphere – it can’t have a large heating affect

This is an attempt to play a classic common-sense card but is completely wrong. In 1856, American scientist Eunice Newton Foote conducted an experiment with an air pump, two glass cylinders and four thermometers. It showed that a cylinder containing carbon dioxide and placed in the sun trapped more heat and stayed warmer longer than a cylinder with normal air. Scientists have repeated these experiments in the laboratory and in the atmosphere, demonstrating again and again the greenhouse effect of carbon dioxide.

As for the “common sense” scale argument that a very small part of something can’t have much of an effect on it, it only takes 0.1 grams of cyanide to kill an adult, which is about 0.0001% of your body weight. Compare this with carbon dioxide, which currently makes up 0.04% of the atmosphere and is a strong greenhouse gas. Meanwhile, nitrogen makes up 78% of the atmosphere and yet is highly unreactive.

4. Scientists manipulate all data sets to show a warming trend

This is not true and a simplistic device used to attack the credibility of climate scientists. It would require a conspiracy covering thousands of scientists in more than a 100 countries to reach the scale required to do this.

Scientists do correct and validate data all the time. For example we have to correct historic temperature records as how they were measured has changed. Between 1856 and 1941, most sea temperatures were measured using seawater hoisted on deck in a bucket. Even this was not consistent as there was a shift from wooden to canvas buckets and from sailing ships to steamships, which altered the height of the ship’s deck – and these changes in turn altered the amount of cooling caused by evaporation as the bucket was hoisted onto deck. Since 1941, most measurements have been made at the ship’s engine water intakes, so there’s no cooling from evaporation to account for.

Also read: A Trip to the Top of the World, Where the Climate Crisis Is All Too Clear

We must also take account that many towns and cities have expanded and so that meteorological stations that were in rural areas are now in urban areas which are usually significantly warmer than the surrounding countryside.

If we didn’t make these changes to the original measurements, then Earth’s warming over the last 150 years would have appeared to be even greater than the change that has actually been observed, which is now about 1º C of global warming.

5. Climate models are unreliable and too sensitive to carbon dioxide

This is incorrect and misunderstands how models work. It is a way of downplaying the seriousness of future climate change. There is a huge range of climate models, from those aimed at specific mechanisms such as the understanding of clouds, to general circulation models (GCMs) that are used to predict the future climate of our planet.

There are over 20 major international centres where teams of some of smartest people in the world have built and run GCMs containing millions of lines of code representing the very latest understanding of the climate system. These models are continually tested against historic and palaeoclimate data as well as individual climate events such as large volcanic eruptions to make sure they reconstruct the climate, which they do extremely well.

No single model should ever be considered correct as they represent a very complex global climate system. But having so many different models constructed and calibrated independently means that we can have confidence when the models agree.

Also read: India Must Stop Deforesting Its Mountains If It Wants to Fight Floods

Taking the whole range of climate models suggests a doubling of carbon dioxide could warm the planet by 2º 4 to 5º C, with an average of 3.1º C. All the models show a significant amount of warming when extra carbon dioxide is added to the atmosphere. The scale of the predicted warming has remained very similar over the last 30 years despite the huge increase in the complexity of the models, showing it is a robust outcome of the science.

By combining all our scientific knowledge of natural (solar, volcanic, aerosols and ozone) and human-made (greenhouse gases and land-use changes) factors warming and cooling the climate shows that 100% of the warming observed over the last 150 years is due to humans.

There is no scientific support for the continual denial of climate change. The Intergovernmental Panel on Climate Change (IPCC), set up by the United Nations to openly and transparently summarise the science, provides six clear lines of evidence for climate change. As extreme weather becomes more and more common, people are realising that they do not need scientists to tell them the climate is changing – they are seeing and experiencing it first hand.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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• Climate change

Image source, Frans Lemmens

Scientists and politicians say we are facing a planetary crisis because of climate change.

But what’s the evidence for global warming and how do we know it’s being caused by humans?

How do we know the world is getting warmer?

Our planet has been warming rapidly since the dawn of the Industrial Revolution.

The average temperature at the Earth’s surface has risen about 1.1C since 1850. Furthermore, each of the last four decades has been warmer than any that preceded it, since the middle of the 19th Century.

These conclusions come from analyses of millions of measurements gathered in different parts of the world. The temperature readings are collected by weather stations on land, on ships and by satellites.

Multiple independent teams of scientists have reached the same result – a spike in temperatures coinciding with the onset of the industrial era.

Image source, ReutersImage caption, Turkey was one of the places hit by devastating wildfires this summer

Scientists can reconstruct temperature fluctuations even further back in time.

Tree rings, ice cores, lake sediments and corals all record a signature of the past climate.

This provides much-needed context to the current phase of warming. In fact, scientists estimate the Earth hasn’t been this hot for about 125,000 years.

How do we know humans are responsible for global warming?

Greenhouse gases – which trap the Sun’s heat – are the crucial link between temperature rise and human activities. The most important is carbon dioxide (CO2), because of its abundance in the atmosphere.

We can also tell it’s CO2 trapping the Sun’s energy. Satellites show less heat from the Earth escaping into space at precisely the wavelengths at which CO2 absorbs radiated energy.

Burning fossil fuels and chopping down trees lead to the release of this greenhouse gas. Both activities exploded after the 19th Century, so it’s unsurprising that atmospheric CO2 increased over the same period.

Image source, Getty Images

There’s a way we can show definitively where this extra CO2 came from. The carbon produced by burning fossil fuels has a distinctive chemical signature.

Tree rings and polar ice both record changes in atmospheric chemistry. When examined they show that carbon – specifically from fossil sources – has risen significantly since 1850.

Analysis shows that for 800,000 years, atmospheric CO2 did not rise above 300 parts per million (ppm). But since the Industrial Revolution, the CO2 concentration has soared to its current level of nearly 420 ppm.

Computer simulations, known as climate models, have been used to show what would have happened to temperatures without the massive amounts of greenhouse gases released by humans.

• What does net zero mean?
• Is the UK on track to meet its climate targets?

They reveal there would have been little global warming – and possibly some cooling – over the 20th and 21st Centuries, if only natural factors had been influencing the climate.

Only when human factors are introduced can the models explain increases in temperature.

Image source, Getty ImagesImage caption, The number of weather-related disasters has increased by a factor of five over 50 yearsWhat impact are humans having on the planet?

The level of heating Earth has experienced already is predicted to cause significant changes to the world around us.

Real-world observations of these changes match patterns scientists expect to see with human-induced warming. They include:

• The Greenland and Antarctic ice sheets melting rapidly
• The number of weather-related disasters has increased by a factor of five over 50 years
• Global sea levels rose 20cm (8ins) in the last century and are still rising
• Since the 1800s, the oceans have become about 40% more acid, affecting marine life

But wasn’t it warmer in the past?

There have been several hot periods during the Earth’s past.

Around 92 million years ago, for example, temperatures were so high that there were no polar ice caps and crocodile-like creatures lived as far north as the Canadian Arctic.

At times in the past, sea level was 25m (80ft) higher than the present. A rise of 5-8m (16-26ft) is considered enough to submerge most of the world’s coastal cities.

There is abundant evidence for mass extinctions of life during these periods. And climate models suggest that, at times, the tropics could have become “dead zones”, too hot for most species to survive.

These fluctuations between hot and cold have been caused by a variety of phenomena, including the way the Earth wobbles as it orbits the Sun over long periods, volcanic eruptions and short-term climate cycles such as El Niño.

For many years, groups of so-called climate “sceptics” have cast doubt on the scientific basis of global warming.

However, virtually all scientists who publish regularly in peer-reviewed journals now agree on the current causes of climate change.

A key UN report released in 2021 said it “is unequivocal that human influence has warmed the atmosphere, oceans and land”.

The COP26 global climate summit in Glasgow in November is seen as crucial if climate change is to be brought under control. Almost 200 countries are being asked for their plans to cut emissions, and it could lead to major changes to our everyday lives.

• Six ways the UK could tackle climate change
• Why the COP26 climate summit is important
• What will climate change look like for you?
• Will the UK meet its climate targets?
• How extreme weather is linked to climate change

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