Is Climate Change Our Fault…

I have had recent correspondence asking me my view on Climate Change. I wouldn’t give my opinion but asked the commenter to say what they thought or had heard. They replied in some detail – although I am assured that there is more to come. I have asked if I could address a couple of the points in a post not just in the comments and he has agreed.

Firstly, we agreed that climate change is happening. The planet is warming up, the oceans most of all, and this is affecting our climate. What is not so obvious is what is causing this. He wrote…

Well Sir, obviously climate change is happening in some form or another. For me the question is, “Are we entirely responsible for it?” You see this has happened before quite recently and it has been much worse than it is now. In Henry VIII’s time, they were roasting cattle on the Thames and everything was frozen. They had a very minor ice age! But even more recently it has been evident. In 1875 England went crazy! They were bringing in their harvest at Christmas and there was snow in June.

The argument goes that because there has been variability in the climate in the past, the current trend is therefore most likely a natural phenomenon. Climate scientists know that the climate has changed over time (it’s what they do for a living) and they use various techniques to analyse why the changes occur. In recent history there has been the Medieval Warm Period (MWP AD 1000 to AD 1300) and the Little Ice Age (LIA AD 1400 to AD 1900) and the current climate trend is often compared to these. The MWP applied to parts of the northern hemisphere but scientists have good reason to believe that other parts of the globe were significantly cooler. Averaging this out over the whole planet leads to a global temperature lower than we are currently experiencing. We also know why the MWP was warm because it coincided with a period of high solar output and unusually low volcanic activity (volcanoes tend to have a cooling effect on climate).

Nobody seems quite sure why the LIA occurred although it did coincide with higher than normal volcanic activity and variable solar output. Scientists are sure that from the end of the LIA to the 1950s the Sun’s output has been high and this is probably what caused the LIA to end. Since the 1950s the Sun’s output has been in decline, but the global temperature has continued to rise. This is part of the evidence that human activity is to blame for our current predicament.

So in summary it is not uncommon but the issue now is that…we have nothing to compare it against as the problems in the past have not been well documented…so I believe we have contributed to climate change but due to our lack of knowledge about the world, we can not say how much.

Climate scientists are able to say a lot about past climate even though practical records do not go back that far. They use things called proxies. A proxy is something that stands in for something else, so in this case they can look at other things that can be measured and which we know are directly affected by climatic conditions. For example, high solar output causes the radioactive isotope of carbon (carbon14) to be produced in the upper atmosphere. If we want to know about solar output in the past we just need to find some fossilised plant material of the appropriate age and measure its C14 value. Higher than expected would correspond to high solar output, lower levels would suggest lower solar output. The great thing about these methods is that they can be compared against one another. If they produce a similar story then it is reasonable to assume that the underlying science is sound. Comparing stalactite rings and tree ring data with other estimates of temperature help to show the trend. I wrote about the self-correcting nature of science in a post called Jolly Hockey Sticks some years ago.

I am not an expert in this subject, but there are experts out there who have devoted their lives to the study of climate. The experts then collaborate and share their findings so that yet further scientists and statisticians can combine the information to present a consensus. Even though it seems amazing, we do know a great deal more about the past than was recorded at the time, and any argument against man-made global warming has to bash down a mountain of overwhelming contradictory evidence.

There is some good stuff on Twig Prep about climate science. Click on this link to be automatically logged in as an anonymous user then click here to see a few thoughtfully constructed videos.

Questions…

1. What does the word theory mean when used by scientists?
2. What is a fair test?
3. If an experiment is described as controlled, what does this mean?
4. What is the difference between the independent and dependent variable in an experiment?

If you want to push yourself a little harder, the following is a ten minute video on why the “It’s all natural” argument is false. It is quite technical but very well constructed.