#TalkAboutIt: Climate change sceptics versus the scientists

Updated

Organisers of the Paris climate conference hope the upcoming summit will lead to a new agreement on reducing global greenhouse gas emissions, thereby limiting climate change in the long term.

Australia, which announced plans to cut emissions by 26-28 per cent by 2030, is expected to join nearly 200 countries at the talks in December.

But despite the push for collective action, scepticism remains in some quarters.

Here are five common claims from those who believe that climate change is not man-made and global warming is a myth.

Claim 1: Global warming is not happening because it is cold

"The idea that global warming is over because you encounter a cold day is a very common mistake people make," said Matthew England, climate scientist from the University of New South Wales and a fellow at the Australian Academy of Science.

"We experience 'weather', that's what you respond to physiologically," Professor England said.

"'Climate' is very different, it's the average of all of the weather over a year or a season, and climate change is about the change in those averages over decades to a century.

"The climate system is changing dramatically compared to past climate changes ... and yet humans go about their day-to-day activity really responding to the weather."

The UN panel of climate experts, the Intergovernmental Panel on Climate Change (IPCC), reported in 2013 no increase in global temperatures since 1998 despite rising man-made greenhouse gas emissions.

But the latest, updated research instead shows no pause in the earth's warming, with 10 of the hottest years on record having happened in the past 17 years.

Data from space agency NASA and the US National Oceanic and Atmospheric Administration (NOAA) found 2014 was the hottest year in modern history.

And this week it announced July was the warmest month since record-keeping began in 1880, with 2015 shaping up to beat last year's mark.

"The new analysis suggests no discernible decrease in the rate of warming between the second half of the 20th century, a period marked by man-made warming, and the first 15 years of the 21st century," experts led by NOAA wrote in the journal, Science.

Parts of the world that saw record heat included Russia, the western United States, parts of South America and Australia, north Africa and most of Europe.

"While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases," said Gavin Schmidt, director of NASA'S Goddard Institute of Space Studies.

Claim 2: Climate has changed throughout the earth's history

There have been huge climate changes in the past, notably during the ice age when massive ice sheets thickened and expanded over the Arctic region, the Antarctic and Greenland.

"The Ice Age cycles were triggered by very subtle wobbles in the earth's tilt," Professor England said.

"If you look at the 'forcings' we're applying today, and the rate of change in the climate system, this change that we're imposing with greenhouse gases is about a thousand-fold the size of the change we had from these orbital shifts.

"No comfort then comes from these past changes. We should be very concerned to see that in the earth's history these very subtle forcings changed the climate in such dramatic ways."

A 2014 study led by the Australian National University shows sea levels remained steady for thousands of years before global industrialisation.

"In the last 6,000 years before the modern onset of sea level rise, the sea level has been quite stable," ANU's Professor Kurt Lambeck said.

"For the last 150 years we've been seeing this increase, this rising sea level, at a rate of a few millimetres per year, and in our older records we do not see similar behaviour," he said.

Professor England warned that adapting to the potential future impacts of climate change would be "astronomically costly."

"Whilst climate has changed in the past, it hasn't changed much at all during human civilisation during this 6,000-year period," he said.

"All the infrastructure we've built — that's going to be the thing of the past.

"Future climate is going to be so different that we're going to have to re-engineer so much of what we've built and that's a very costly process: to re-engineer train lines to allow for excessive heat wave days, to re-engineer our coastlines to deal with rising sea levels, to move whole cities that are no longer viable with a metre of sea level rise."

Claim 3: Human emissions are tiny compared to natural CO2

Carbon dioxide (CO2), one of the gases that influences climate change, is naturally present in the atmosphere as part of the Earth's carbon cycle.

According to the United States Environmental Protection Agency, CO2 from human activity accounted for approximately 82 per cent of all US greenhouse gas emissions in 2013.

Scientists measure the level of carbon dioxide according to how many molecules of CO2 are floating around in a million molecules of air, or parts per million measurement.

"Human activities are altering the carbon cycle, both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere," it said.

Professor England said greenhouse gases are now 40 per cent higher than they were before the industrial revolution.

"We know with certainty human emissions are the cause of this increase in carbon dioxide," he said.

"There are trillions of tonnes of carbon locked up in fossil fuels. We are burning them overnight and putting those carbon dioxide molecules back into the atmosphere.

"Carbon dioxide levels were incredibly stable before the industrial revolution, they sat at about 280 parts per million globally.

"They're now punching through 400 parts per million. This is a change from 280 units to 400. This has been due to human emissions or human activity that's burnt coal and created extra amounts of carbon dioxide in the atmosphere."

Claim 4: Scientists are creating panic in order to get funding

"This myth is just so absurd," Professor England said.

"Scientists are all about finding out the truth in the climate system. If they could disprove the physics of the greenhouse effect ... they'd be up for a Nobel prize.

"It took the science community a long time to be as vocal as we are today. We've seen 30 or 40 years of projections come true, we've got this whole field of science devoted to making projections and at the moment we're just sitting back and watching them come true."

US and British scientific academies have said there is a clear consensus that climate change is real and will have serious disruptive effects on the planet.

Earlier this year, the US National Academy of Sciences and Britain's Royal Society released a joint declaration aimed at moving the public debate on from whether climate change is happening, to the question of how the world responds.

"It is now more certain than ever, based on many lines of evidence, that humans are changing the earth's climate," the joint publication said.

"The atmosphere and oceans have warmed, accompanied by sea-level rise, a strong decline in Arctic sea ice, and other climate-related changes."

World governments, including Australia and United States, have publicly acknowledged that climate change is real.

"We must take action because humanity does make a contribution," Prime Minister Tony Abbott told the Liberal Party last week.

In January, US Senate Republicans joined Democrats in declaring that "climate change is real and not a hoax."

Claim 5: Antarctic sea ice is growing



In 2014, Antarctic sea ice expanded to unprecedented levels, covering more than 20 million square kilometres for the first time since records began.

Dr Jan Lieser from the Antarctic Climate and Ecosystems Cooperative Research Centre said sea ice growth was a symptom of global warming.

"The increase in Antarctic sea ice extent might seem paradoxical given changes in the global climate, but it's not when we consider some of the other factors at play," he said.

"Fresher water freezes at a higher temperature, and we know that the sea water around Antarctica is becoming less salty partly due to the rapid shrinking of the thick Antarctic ice sheet over land.

"Factors like wind, snowfall and the saltiness of the water all play an important role in this process, and we know that all of these inputs have been changing as part of larger changes in the global system."

Scientists said it was also important to make the distinction between Antarctic sea ice and land ice.

While Antarctic sea has grown in recent years, its ice shelf has shrunk an average rate of about 100 gigatonnes per year.

Professor England said it was the Ross Sea sector, a very small region in the Antarctic, where sea ice is expanding.

"If you look at all of the cryosphere there is melt occurring in all of the systems that we're really concerned about: the Greenland ice sheet, the Antarctic and Arctic ice sheets, the ice over the world's mountain glaciers without exception. They are melting rapidly, raising global sea levels," he said.

"So all of the world's cyrosphere is ringing out the alarm bells, the ice is melting rapidly, globally."

An analogy for this climate scepticism could be "somebody who smokes cigarettes," Professor England said.

"Their health is terrible, their lungs are about to collapse, but you find that the pinky on their finger is in great health, they've got a lovely fingernail there, it's growing beautifully.

"It's grabbing a tiny part of the person's system and saying 'That bit of their body is actually healthy and okay, they're about to collapse from all sorts respiratory problems but hey, this is not a problem'."

ABC/wires

Topics: climate-change, environment, environmental-impact, earth-sciences, australia, asia, pacific, european-union, united-states, antarctica, greenland

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