I would love for Doug Edmeades to be right, as I would sleep better at night, but the arguments he trots out have been debunked over and over again, writes climate scientist James Renwick.

Some memes never die. Every time you shoot them down they just get up again like the zombies they are. “Satellite temperatures show no warming for 20 years” is a classic, as trotted out in an op-ed piece by Doug Edmeades for the NZ Farmer published on Stuff yesterday. This is it just wrong, as a quick Google of “satellite temperatures” could tell anyone. The 20-year thing is chosen because 1998 was a big El Niño year, so warmer than surrounding years, so minimising any upward trend from there. This is known as “cherry-picking”, selecting just the numbers that support your argument and ignoring the rest.

When Invercargill is hitting 32°C, high tides and storm surges inundate Tamaki Drive and wreck the roads around the Coromandel Coast, New Zealand glaciers lose one third of their ice in 40 years, Christmas wildfires in California are followed by massive rain storms and mudslides, it’s easy to see the changing climate. “But is it us?” I hear Doug Edmeades ask. Yes is the rock-solid answer. The only ways to change the climate are to change the brightness of the sun, and/or to change the amount of greenhouse gases in the air. Those two things control the amount of energy the earth’s surface takes in and explain the ice age cycles and all the changes in climate we know of over many millions of years.

In the past century, the sun hasn’t brightened up. In fact it’s become a bit dimmer. Meanwhile, the concentration of carbon dioxide in the air has gone up over 40% since we started burning oil and coal for fuel, the biggest change in the earth’s atmosphere for over 3 million years. We know the increase is down to us burning fossil fuels, because the chemical signature of fossil carbon is different, having lost its radioactive fraction over millions of years underground. Plus, the amount of oxygen in the air is going down as carbon dioxide goes up, a sure sign of burning. Human activity, mostly burning fossil fuels, is the only explanation for the way the atmosphere, and the climate, is changing.

So, over tens of thousands of years, changes in the earth’s orbit can bring on an ice age. Or, over a matter of decades, humanity can put enough carbon dioxide in the air to delay the next ice age indefinitely.

Carbon dioxide stays in the air for centuries, making it the most important greenhouse gas in the long run. Other gases, like methane, are better at absorbing heat but they don’t stay around so long. The most extreme example is water vapour, the stuff that makes clouds and rain when it condenses. A molecule of water vapour absorbs more heat than does a molecule of carbon dioxide, but stays in the air only a matter of days. The only way to get more water vapour in the air is to make the air warmer (it would just fall out as rain otherwise). That means the warming effect of water vapour can only be an amplifier: find a way to warm the climate (such as more carbon dioxide) and water vapour levels will increase, warming the climate more. The water vapour amplifier roughly doubles the warming from an increase in carbon dioxide.

So what about Doug Edmeades’ “sceptical” views?

• Yes, through the ice ages, the sunlight may have changed first. But that has no bearing on a situation where the carbon dioxide is doing the changing. Either one will change the climate.
• Yes water vapour is an important greenhouse gas, but is only a slave to carbon dioxide and sunlight. No one is arguing about how increased water vapour warms the climate – it has been understood for 150 years.
• Yes, parts of the globe had a “medieval warm period” and a “little ice age”, brought on by changes in sunlight and a few well-timed volcanic eruptions (that block out sunlight). The global changes we see today are far more extensive and are caused by increased greenhouse gases (put into the air by us).
• Sea level rise has very obviously accelerated, roughly doubling over the past century and is set to increase more as the big ice sheets really start to melt.
• Satellite estimates of temperature show significant warming over the past 20 years, and in the 40 years since they started. Thermometers at ground level show warming over the past century and more. The earth is now more than 1°C warmer than it was in the 19th.
• Doug says keeps an eye out for evidence. He must have missed the thousands of scientific papers published on climate change over the past few years, and the observations of melting ice, sea level rise, record high temperatures, etc.
• Polar bear numbers are increasing. Strange then that polar bears are now listed as a “vulnerable species”, as a result of climate change. A quick look on Google and Wikipedia can help out here.
• The Intergovernmental Panel on Climate Change (IPCC) has said there is no evidence that extreme weather events are increasing as a consequence of global warming. Not sure where this one comes from Doug. In 2012, the IPCC published a special 500-page report on exactly this topic, citing hundreds of studies that show climate change is leading to increasing extreme events.
• Models are not evidence. They are not observations, but they are a great way to test ideas and to make predictions. Climate models have successfully predicted the cooling effect of big volcanic eruptions (such as Mt Pinatubo in 1991), the onset and development of El Niño and La Niña events, and the evolution of global temperatures over the past century.

Why do these zombie ideas refuse to die, when there’s so much evidence readily to hand? Maybe in part because we love the underdog, the plucky “independent scientist” who confounds the global scientific establishment. I would love for Doug to be right, as I would sleep better at night, and he would be in line for a Nobel Prize for overturning 100 years of research by thousands of scientists. Strange, I’ve never seen his name on the short list.

Maybe another part of the problem is the determined campaign by oil companies to confuse the public and muddy the policy debate around climate change action. The sorts of tactics Doug Edmeades displays are classics of the disinformation campaigns going back decades, to tobacco companies disputing links between smoking and cancer, chemical companies disputing the ozone hole and acid rain, and now oil companies disputing oil burning and climate change. The excellent book Merchants of Doubt by Naomi Oreskes and Eric Conway documents in great detail how this has been done and how successful it has been. I am not saying Doug is paid by Exxon, but he understands that “doubt is our product”.

The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.