Australia's most prominent anti-climate science senator, Malcolm Roberts, used a Senate estimates hearing to ask the country's chief scientist whether he believed carbon dioxide caused by humans affected the climate.
Chief scientist Dr Alan Finkel (who has a PhD in electrical engineering and was a postdoctorate fellow in neuroscience) started from the top and gave one of the most simple, step-by-step explanations of how climate change worked.
Here's how it went:
Across all the countries of the planet we’ve been burning fossil fuels for a rapid rate. It’s clear that by doing that we are emitting ever-increasing carbon dioxide into the atmosphere. The natural systems can’t absorb that. There’s a clear hypothesis, then there’s clear evidence. The thing that I find most compelling, senator, is that when you have a combination of a hypothesis and evidence.
When it comes to carbon dioxide it’s clear what would be driving increases in carbon dioxide, then you go out and measure it. Carbon dioxide goes up every year. Last year carbon dioxide went up 3.05 ppm which is more than any other time.
So the carbon dioxide is going up. Does that create warming? The theory is that carbon dioxide does trap heat, so ultraviolet light comes through the atmosphere without interruption, or almost without interruption, hits the ground, warms the ground and you get an infrared radiation from the ground which is then to some extent trapped by the carbon dioxide.
That theory goes back to 1896, Swedish physical chemist Svante Arrhenius did the initial work on that. He subsequently got a Nobel prize for other work and he identified that back in 1896 that carbon dioxide in the atmosphere, for basic physical reasons will trap heat.
So you’ve got the carbon dioxide, you’ve got the physics that says carbon dioxide would trap heat coming off the ground being radiated from the surface and from the water as well.
Do you have the evidence? Yes!
The temperature is going up and up and up. It was just yesterday that NASA declared that the last 12 months, yet again have been the hottest on record. So in both cases carbon dioxide is going up and it's trapping heat, you’ve got evidence and theory. The second case is that that trapped heat will lead to an increase in temperature, you’ve got the theory and the evidence. That’s steps one and two.
The third step is the impact. The temperatures going up, what will that do to climate? That’s where it gets very, very difficult now you’re into the world of modelling.
Roberts, who sits on the Australian Senate's crossbench with Pauline Hanson's One Nation party, then threw Finkel a follow up.
Senator Roberts: For whose data do you rely on your statement that the temperature is going up and up and up?
Dr Finkel: Everybody senator. NASA is very reliable because NASA over the years has taken the combination of thousands of terrestrial recording sites and their satellite recordings and with great consistency they’re seeing the temperature going up. Then you’ve got the UK Bureau of Meteorology. The National Ocean and Atmospheric Organization in America. You’ve got our bureau. Pretty much every organization in the world.
Senator Roberts: Pretty much every organization in the world?
Dr Finkel: Well, every major scientific organization.
Senator Roberts: Every major scientific organization in the world.
Roberts asked for a written "summary of the logic you've just outlined and the empirical evidence at each stage". Finkel, smiling, replied, "I can certainly give it a try".
Mark Di Stefano is a media and politics reporter for BuzzFeed News and is based in London.
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