In his first week in office, President Trump has overturned President Obama’s stopping of two pipelines and has indicated a strong preference for further oil drilling. He has also denied that climate change is real. For me, this raises two issues. The first is, will President Trump’s denial of climate change, and his refusal to take action, make much difference to climate change? In my opinion, not in the usual sense, where everybody is calling for restraint on carbon dioxide emissions. The problem is sufficiently big that this will make only a minor difference. The action is a bit like the Captain of the Titanic finding two passengers had brought life jackets so he confiscates them and throws them overboard. The required action was to steer away from a field of icebergs, and the belief the ship was unsinkable was just plain ignorant, and in my opinion, the denial that we have to do something reasonably dramatic about climate change falls into the same category. The second issue is how does science work, and why is it so difficult to get the problem across? I am afraid the answer to this goes back to the education system, which does not explain science at all well. The problem with science for most people is that nature cares not a jot for what you feel. The net result is that opinions and feelings are ultimately irrelevant. You can deny all you like, but that will not change the consequences.
Science tries to put numbers to things, and it tries to locate critical findings, which are when the numbers show that alternative propsitions are wrong. It may be that only one observation is critical. Thus Newtonian mechanics was effectively replaced by Einstein’s relativity because it alone allowed the calculation of the orbital characteristics of Mercury. (Some might say Eddington’s observation of light bending around the sun during an eclipse, but Newton predicted that too. Einstein correctly predicted the bending would be twice that of Newton, but I think Newton’s prediction could be patched given Maxwell’s electrodynamics. For Newton’s theory, Mercury’s orbit was impossible to patch.)
So what about climate change? The key here is to find something with the fewest complicating factors, and that was done when Lyman et al. (Nature 465: 334-337, 2010) measured the power flows across ocean surfaces, and found there was a net input of approximately 0.6 W/m2. That is every square meter gets a net input of 0.6 Joules per second, averaged over the 24 hr period. Now this will obviously be approximate because they did not measure every square meter of ocean, but the significance is clear. The total input from the star is about 1300 W/m2 at noon, so when you allow for night, the fact that it falls away significantly as we get reasonably away from noon, and there are cloudy days, you will see that the heat retained is a non-trivial fraction of the input.
Let us see what that means for the net input. Over a year it becomes a little under 19 MJ for our square meter, and over the oceans, I make it about 6.8 x 1021 J. There is plenty of room for error there (hopefully not my arithmetic) but that is not the point. The planet is a big place, and that is really a lot of energy: about a million million times 1.6 tonnes of TNT.
That has been going on every year this century, and here is the problem: that net heat input will continue, even if we totally stopped burning carbon tomorrow, and the effects would gradually decay as the carbon we have burnt gradually weathers away. It would take over 300 years to return to where we were at the end of the 19th century. That indicates the size of the physical problem. The fact that so many people can deny a problem exists, with no better evidence than, “I don’t believe it,” is our current curse. The next problem is that just slowing down the production of CO2, and other greenhouse gases, is not going to solve it. This is a problem that has crept up on us because a planet is a rather large object. It has taken a long time for humanity’s efforts to make a significant increase to the world’s temperatures, but equally it will take a long time to stop the increase from continuing. Worse, one of the reasons the temperature increases have been modest is that a lot of this excess heat has gone into melting ice. Eight units of water at ten degrees centigrade will melt one unit of ice, and we end up with nine units of water at nought degrees Centigrade. The ice on the planet is a great restraint on temperature increases, but once the ice in contact with water has melted, temperatures may surge. If we want to retain our current environment and sea levels, we have some serious work to do, and denying the problem exists is a bad start.