Hopefully it’s not news to you that the Earth is warming due to human release of carbon dioxide and other greenhouse gases. A number of studies have assessed the scientific consensus on anthropogenic global warming (AGW), with results clustering around 97%. Overwhelmingly, most climate scientists have looked at the data and concluded that AGW is happening.

Climate scientists have gone beyond just establishing that AGW is happening. They are trying to quantify it and project the trend lines into the future. This type of effort is always fraught with uncertainty, with the error bars increasing with greater time into the future. However, we can take a 95% confidence interval and make reasonable extrapolations of what is likely to happen.

Recognizing this uncertainty, the Intergovernmental Panel on Climate Change (IPCC) has concluded that we should keep post-industrial warming to less than two degrees Celcius if we want to avoid serious effects of climate change. Given that as the goal, they can then determine how much more carbon would need to be released to cause this amount of warming. This can be used to determine how much we need to decrease future carbon emissions.

Primarily those with an ideological or financial stake in denying this solid consensus focus on the uncertainty. But that is folly. Phil Plait has a good analogy – if 97% of the world’s astronomers were in agreement that there was a 95% chance of an asteroid hitting the Earth in 2050, would you be listening to the 3% of dissenters? If NASA and other experts were mostly saying that it will take 20 years to develop the technology to deflect the asteroid, and the earlier we do it the more effective our attempts will be, do you think it would be prudent to argue for waiting a couple of decades to see what happens? Maybe the asteroid is not as big as they say. Maybe it will hit in a remote area and not do that much damage. It may cost less to fix the damage than divert the asteroid. Asteroids deliver useful metals to the Earth’s surface, so this could be a good thing. Don’t listen to the asteroid hysterics. The motivated reasoning is transparent.

Denial aside, we are now getting to the point that simple math is constraining our options. We have to reduce our carbon release quickly in order to avoid the 2 degree C warming. We can argue about how quickly, but we are actually just arguing about how long it will take for the worst outcomes to be manifest. It is not a question of if, but of when. We can hope for the best outcome, but should plan on the 95% confidence interval.

Those same scientists, however, are saying essentially that it is highly unlikely we will be able to reduce CO2 emissions quickly enough. We will certainly not do it if current trends continue – the math just does not work. Still we need to do everything we can – increase energy efficiency, shift to renewable energy, and reduce fossil fuel use.

Another option is carbon capture – remove carbon from the atmosphere to offset the new carbon being released. Here the IPCC has a dilemma. They have charted all possible pathways to avoid the 2 degrees warming, and they have concluded that essentially we cannot do it through reduction of emissions alone. In the second half of the 21st century we will need to remove a significant amount of carbon from the atmosphere, about 12 billion tons per year, or a third of the current rate of release.

However by focusing on carbon capture they worry that people will see such technologies as the ultimate solution, and therefore we don’t have to worry about reducing carbon release. So now they are also emphasizing that carbon capture will not be enough. We need to do both – reduce emissions and carbon capture.

This is where another layer of thinking comes in – techno-optimism. There are those who argue that we will technology our way out of this dilemma. Renewable energy technology will advance and replace dirty old energy technology. We will also develop high-tech carbon capture technology and take care of all that extra carbon. I am sympathetic toward this attitude, but I also agree that we cannot rely on technological advances we haven’t made yet. These are always hard to predict. Again – hope for the best, but prepare for the worst. We can’t just assume that in 30 years we will develop a technology to deflect the asteroid.

But what is the state of carbon capture? One approach is essentially to use plants, specifically trees. Trees are natural carbon capture devices. There are already efforts at reforestation, and to reduce deforestation, and they should continue. But this will not really address the problem. There isn’t enough land to simply plant trees to capture carbon, and trying to use lots of land for this approach will likely be counterproductive.

There is one company, Climeworks, that uses artificial filters to capture carbon. They have one factory that currently captures 1000 tons of carbon per year. If you remember from above, we would need about 12 million of these to reach our goal. That is why the IPCC is now saying we cannot rely on this technology alone. How much space would all that carbon capture require?

The company calculated how many shipping container-sized units would be needed to capture 1% of global emissions; the answer was 750,000.

So again, multiply that by about 30 for what we would need.

The technology works by using fans to blow air over filters which capture carbon dioxide. When the filters are full they can be heated to release the carbon in solid form. That solid carbon can be buried or used for industrial use – you can combine it with hydrogen to make plastics or fuel, for example.

It seems that some such technology will be necessary to reach our goal of limiting warming to 2 degrees C. This technology at least works, but it is primitive. It seems prudent to encourage development of this technology. One way to do that is to put a price on carbon. I agree with those who argue that this makes sense and is fair, since releasing carbon has a cost to the world, those who release the carbon should share in that cost. They could, however, offset that cost by also building carbon capture facilities, or buying carbon credits from those who do.

Make a carbon capture industry cost effective, and it is likely the technology will advance and be adopted. Then we might technology our way out of this.

While I remain hopeful, maybe even optimistic, I realize that the math currently looks bad. We cannot get complacent. Now really is the time to shift to renewable energy, to focus on energy efficiency, and to put a proper and fair price on carbon to encourage a carbon capture industry. This is a win win – we will end up with a better energy infrastructure, and a better environment.