When you discuss the risks and consequences of global warming in the public sphere it will often turn to how certain it is. Which is quite strange as there’s a scientific consensus of 97%, this is the percentage of climate scientists who agree that humans are causing global warming.

This is confirmed by several peer-reviewed studies that have found the same overwhelming agreement on this. A 2009 survey of Earth scientists found that among climate scientists actively publishing climate research, 97% agreed that humans were significantly raising global temperature. A 2011 analysis of scientists’ public statements about climate change found that among those who had published peer-reviewed climate research, 97% accepted human-induced warming. The most recent one was a 2013 analysis that examined 11,944 abstracts and again found this 97% consensus.

The same kind of certainty we find when we then take a look at the risks.

If we continue on the current business as usual scenario we can expect our planet to warm between 2.5 and 7.5°C (most likely 5°C) by 2100. This is based on the IPCC RCP8.5 emission scenario where atmospheric CO 2 levels will reach around 1,000 ppm by 2100. The important detail about this is that the last time CO 2 was this high was during the Eocene Climatic Optimum (EECO), which was the warmest period in the last 50 million years.

During that period the planet was completely ice-free (sea-levels were +/-65m higher than today) and recent research puts global temperatures at +/-13°C warmer than today (Cabellero and Huber, 2013). Granted 5°C of that warming was due to changes in the positions of continents, vegetation, and the loss of continental ice sheets. But at +/-8°C and such sea levels eventually that much higher it’s a vastly different world.

It’s this kind of research that informs us that the consequences this century will be severe. Just looking at the recent IPCC report and it’s summary of what this will mean for crop yields shows that we have some serious challenges ahead if don’t do anything:

This is what makes the discussions about risk and certainty so strange. We know it’s happening and we know the consequences will be severe. Current research and reconstructions of past climates is what gives scientists and experts the confidence to say this. It also informs us that if we start acting we can prevent the worst of it. Yes, we’re committed to some warming, but if we act we can deal with that without too much trouble.

A good part of what we know about what can happen is because of the skill our current climate models have. They are incredible in what they already can do and are remarkably accurate when you compare them to past and present changes in climate. It’s also these models that tell us that there is hope. They show two very different futures when you compare action versus inaction. Gavin Schmidt gave a good talk about this and the choice we have:

And here’s where Judith Curry enters the picture. She’s known for her argumentation that there’s just too much uncertainty to act (ignoring the point that uncertainty is not your friend in these cases). When asked about what the projected increases in atmospheric CO 2 levels would mean she said the following:

I don’t know how concerned I should be about it — on what time scale that might happen, whether that’s 100 or 200 years, what societies will be like, what other things are going on with the natural climate,” Curry says. “I just don’t know what the next hundred or 200 years will hold, and whether this will be regarded as an important issue. I just don’t know.

A really strange argument considering what we already know. But it gets even stranger when you see the following from her blog post ‘Atlanta’s 2″ catastrophic snowfall‘ (bolding hers, archived here). In it she talks about the consequences of not acting on uncertain weather predictions:

The rain/snow demarcation was a tough call, as it often is with temperatures right around freezing. It seems that the forecasts were good enough to have triggered a response prior to the onset of the storm. Excerpts from the Weather Underground article: To hear the public officials tell it, they were caught off-guard by the storm, so somewhere in that communications system there was a serious disconnect. The decision-makers either didn’t get the message, or more likely, didn’t have appropriate action plans, which the threatening forecast would have triggered. A major city, along with the state in this case, in spite of direct communications with the National Weather Service, is unable to put the pieces together to understand the RISK to their citizens. Risk implies uncertainty, and understanding it is at the heart of decision-making. Let’s say the chance of the storm producing 3 inches of snow was 30% on Monday, which sounds about right. The Georgia decision-makers didn’t understand that a 30% risk of a cataclysm requires major affirmative action. You can’t wait for a guarantee. How about a 20% chance of tens of thousand of people being stranded on the highway in freezing temperatures? Is that enough for a governor or mayor to make the decision to tell people to stay home? It’s not easy, but it’s not rocket science. Mostly, you have to understand the ingredients that have to come together to create a disaster in your city. (See formula above.) Somewhere and somehow somebody has got to take the lead on closing the threat-understanding gap between forecasters, decision-makers, and the public. It’s not simple because of the division of responsibilities between various federal, state, and local agencies in a disaster. But, we’ve seen too many instances where good-enough weather forecasts have lead to bad decisions and poor public communications. The issue is partly science, which we should be able to solve with an organized effort by the National Weather Service, FEMA, and others.

She’s citing an article where a 30% risk of a “cataclysm” should have required “major affirmative action. You can’t wait for a guarantee.” She summarizes this at the end of her article with the following:

These two statements from the Weather Underground article sum up the situation IMO: Somewhere and somehow somebody has got to take the lead on closing the threat-understanding gap between forecasters, decision-makers, and the public. But this isn’t going to help unless you have an action plan that is developed prior to the event trigger: . . .or more likely, didn’t have appropriate action plans, which the threatening forecast would have triggered.

The hypocrisy here is that she said that in the case of this snow storm that it “was a tough call [… but] It seems that the forecasts were good enough to have triggered a response prior to the onset of the storm.” This is with her quoting an article that said that there was a 30% chance that this storm would have been disruptive.

Yet when she talks about the risks of global warming she says that there’s just too much uncertainty. Despite the 97% of experts saying that it is happening and warning us that we should do something. I truly don’t understand this disconnect between these two positions. Although what bothers me most is that people still listen to her despite this risk hypocrisy (and others making the same claims), statements that aren’t based on what is in the scientific literature.

Although how to solve that? I have no idea.