How to talk to a climate sceptic

G Magazine

Sorting the truth from the trash with our handy guide to busting climate change myths.

Radio shock jocks and the likes of Tony Abbott and Lord Monckton are not the only climate sceptics out there. Chances are, you know some ordinary, everyday people who remain unconvinced about the reality of climate change and the need to do something about it. Here’s a useful summary of the facts and peer-reviewed scientific evidence in answer to the most common myths and misinformation. Let the dinner debates begin!

“So last year was the warmest on record – one freak year doesn’t prove that global warming is happening.”

There is solid evidence of increasing average global surface temperatures over a long period of time.

The UN World Meteorological Association reports that 2010 tied with 1998 and 2005 as one of the warmest years on record. Independent records show the Earth’s average surface temperatures have risen steadily over the last century. The average global surface temperature in 2005 was 0.74ºC warmer than in 1906. The oceans have absorbed much of this additional heat, impacting underwater ecosystems by, for example, affecting algae that grow on the underside of sea ice, which has effects right along the food chain. Global warming is recognised by reputable agencies such as NASA, the CSIRO and the UN as a clear and alarming trend. Sometimes sceptics argue that 100 years’ of recorded temperatures is too short a period from which to draw global warming conclusions – but readings from bubbles of air trapped in ice cores from the Antarctic indicate higher temperatures now than at any other time over the last 100,000 years.

“Carbon dioxide isn’t evil, it’s natural. Trees need it to grow, and rises in it are not the result of human activities.”

Reliable records show that there’s more CO2 in the atmosphere than any time in the last 650,000 years.

Carbon dioxide (CO2) is the second-most potent greenhouse gas after methane, and as our population increases, the amount of CO2 emissions being added to the atmosphere by humans increases by about 30 billion tonnes per year. The oceans are our biggest carbon reservoir but they’re almost at capacity partly as a result of ocean acidification. When the second wave of the Industrial Revolution took off in 1850, the concentration of CO2 in the atmosphere was 280 parts per million (ppm), a level that had been more or less maintained throughout human history. In just 160 years, that’s risen to 390 ppm CO2. According to the journal Science, the last time the Earth had so much carbon in the atmosphere was 20 million years ago. Sea levels after sustained periods of high levels of CO2 were 40 m higher than they are today; temperatures as much as 10ºC hotter. A 2009 paper in the journal Nature concluded that being above 350ppm CO2 threatens the life support systems the planet has developed over the last million years, putting modern human society at risk. A red herring sceptics like to toss into the mix is that lots of the CO2 in the air comes from volcanoes. True, but humans emit over 100 times more CO2 than volcanoes. There’s a smooth and regular trend in the increase of atmospheric levels of CO2 - it doesn’t spike for each volcanic eruption.

“Scientists can’t seem to agree on whether climate change is even happening, so why should I believe it?”

Peer-reviewed scientists have reached a consensus on the facts, and they agree that man-made climate change is real.

All the facts we’ve given you in this article, and always give you in G, are consistent with the scientific consensus on climate change – indeed 97 per cent of climate experts agree that global warming is happening and humans are responsible. There’s nothing wrong with being a little sceptical about the information you hear – there are some scientists who will comment on topics that are out of their field of experience, for various reasons. In Merchants of Doubt, authors Naomi Oreskes and Erik M. Conway liken this to “asking an Air Force captain to comment on the design of a submarine. He might know something about it; then again, he might not. In any case, he’s not an expert.” An example of a reliable source is the world’s leading climatologist, James Hansen of NASA, who in 2007 gave a talk to the American Geophysical Union in which he stated that millions of years of records show that a safe number of CO2 for us now would be 350ppm at the very highest. It’s also important to remember that the very nature of science is that nothing can be absolute: there is always the potential for new findings to change the results. Therefore, experienced scientists will always appeal to this possibility by using words such as ‘may’ and ‘might’ instead of more concrete terms, so they appear to be hesitant when, in fact, they are not.

“The planet will be able to deal with it.”

Maybe some ecosystems will be able to adjust if we don’t reach certain ‘tipping points’ – but will humans be able to survive?

Nature can surprise us with resilience; plants and animals are moving their home ranges and changing their normal habits (not out of choice, but out of necessity). But there are ‘tipping points’ which the Intergovernmental Panel on Climate Change (IPCC) says we’re on the cusp of reaching, after which there is no turning back. Even if greenhouse gas emissions stopped today, the planet would continue to warm because there are so many greenhouse gases in the atmosphere – experts estimate warming could continue for up to 1,000 years. Meanwhile, humans are driving extinction faster than other species can evolve. As the human population increases exponentially, our impact on the planet is amplified. What will this mean for the future of the human species? The predictions are alarming. A warmer atmosphere is expected to lead to an increase in extreme weather events worldwide. The World Health Organisation anticipates an extra several hundred million people would be at risk of contracting malaria with a global temperature rise of 2–3ºC. Our food supplies aren’t secure; we’ll have trouble growing crops in some areas, with developing countries being particularly hard hit. We won’t be able to look to the oceans to feed us either, as we’ve overfished them, and ocean acidification means the growth of many sea creatures is also being affected.

“Who cares about a sea level rise of a few centimetres – that’s nothing!”

It might not sound like much, but it is.

In the last century sea levels have risen at an average of 1.7 mm per year, and this rate is now accelerating. Sydney’s coastline is expected to experience a 40 cm rise in sea levels by 2050. If you still think that sounds like a mere drop in the ocean, consider that even a one-centimetre sea level rise can cause erosion of up to one metre. The Great Barrier Reef protects over 2,000 km of the Australian coastline from the open sea, but rising sea water temperatures are causing the coral reefs to die, so they’ll no longer be able to provide a natural storm erosion buffer. Furthermore, if the Greenland ice sheet (thought to be more than 110,000 years old) melts altogether, we can expect sea levels to rise around seven metres. According to the Environmental Justice Foundation, there could be as many as 150 million climate refugees by 2050. A few centimetres over a few years might not sound like much, but look to the future consequences and you’ll see a huge impact.

“Global temperatures are supposed to fluctuate naturally – we go in and out of ice ages all the time, so it’s a natural cycle.”

The current rate of change is not normal.

While there have been seven cycles of glacial advance and retreat in the last 650,000 years (with the last ice age ending 7,000 years ago), the IPCC says the rate at which the planet is currently warming is unprecedented in the last 1,300 years. The ability of greenhouse gases, including CO2, to trap heat in the Earth’s atmosphere has been accepted since the mid-19th century; a huge increase in the second most potent greenhouse gas – CO2 – will surely affect the planet’s climate. Yes, the Earth does naturally cool and warm, but each time this has happened in the past there has been a natural cause, such as small variations in the Earth’s orbit. The cause of current climate change is CO2, with around 30 billion tonnes of it being pumped into the atmosphere every year by humans. There are other greenhouse gases too – such as methane, which is 25 times more potent as a greenhouse gas than carbon dioxide. Methane levels have more than doubled since the early 1800s, and half of current emissions come from landfill, agriculture and coal mining.

“Some places are actually getting colder – what about the cold snaps across Europe and America?”

Weather and climate are not the same thing.

Short-term weather events are very different from long-term climate trends, which are measured over decades or more – and long-term records do show more extremes and warming temperatures. Weather patterns are changing around the globe as a result of climate change – making it colder in some places, and warmer in others, but a few single data points can’t be taken on their own from small regions, trends must be taken on a whole over larger areas. Look to reputable agencies such as NASA (http://climate.nasa.gov), the Climatic Research Unit (www.cru.uea.ac.uk), the Hadley Centre (www.metoffice.gov.uk/climate-change) and the CSIRO (www.csiro.au/science/Changing-Climate) for reliable information on climate trends. The CSIRO has just published a free online resource on climate change science, available at www.csiro.au/Climate-Change-Book.