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Jonathan Gravestock & Howard Curnow


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These pieces appeared in the Methodist Recorder, 11 and 25 Jan 19, and are republished here by permission.


The Rev. Howard Curnow asked two questions in his letter (Recorder, 14 Dec):

1. If carbon dioxide is the driver of climate change, why has its steadily increasing atmospheric level not been exactly mirrored by global temperature?

2. Since many factors cause climate change, why is CO2 now assumed to be the only one?

His second question partially answered his first; that the relationship is complicated by theer being many factors that govern global temperature, the most significant of which is perhaps variation in solar activity.

Also, comparisons over a few decades, such as he mentions, are like concluding that one person who smokes all their life without developing lung cancer proves smoking to be safe. More meaningful comparisons have been made by analysing gas trapped ini bubbles within ice sheets, which have shown correlation between CO2 levels of around 200ppm and ice ages, as opposed to 280 ppm during inter-glacial periods, over almost half a million years.

The answer to his second question is that while CO2 is not the sole cause driving global warming, it is the cause over which humanity has most control. Mr. Curnow is right in saying both that correlation is not causation and that some scientists dispute the link between global warming and CO2 levels. It is also true, however, that there is now more evidence that increased CO2 levels and global temperatures are linked than that smoking and lung cancer are.

I was studying pathology in the early 1970s when widespread warnings were first published in "Smoking and Health Now"; warnings thtat were challenged by the tobacco industry's scientists. Those warninigs included one that it takes 10 years after quitting smoking to return to your pre-smoking risk level.

Current estimates predict that if we fail to stop burning all the world's existing fossil fuel reserves, global temperatures will not return to existing levels for tens of thousands of years. With the benefit of hindsight over smoking, is that a risk worth taking or should we rather be promoting the health of our wonderful home and heritage?

JG, East Sussex.


Howard Curnow's reply:

It seems somewhat strange to me that in his letter (11 Jan), Jonathan Gravestock criticises me for looking atn temperature levels over "a few decades" (the whole of the 20th century) when the whole AGW theory grew originally from looking at less than three decades at the end of the last century, ignoring the earlier decades.

He also mentions "evidence that increased CO2 and global temperature are linked". My understanding is that ice core research, which he refers to, incates that down the ages, temperature changes have preceded changes in CO2 levels - the opposite to what Al Gore claimed in his film "An Inconvenient Truth" a few years ago.

That slowly rising temperatures are being driven mainly by CO2 rises is an assumption built into most computer climate models used to predict future temperatures, and when past predictions are compared to actual present temperatures, they are all seen to over-estimate the expected rises. That fact should surely lead to questioning whether the models have exaggerated the extent to which CO2 levels are responsible for rising temperatures.

I have been re-reading Justin Thacker's article (Recorder, 14 Dec). I can understand where he is coming from and his very real concerns for the poor, but part of his article appalled me: he wrote "...climate change increases the risk of heat waves - and as well as killing people directly, these lead to an increased risk of forest fires, increasing the severity of floods and droughts, lead to crop failures and malnutritiion and increase the spread of mosquito-borne diseases such as malaria". What proof does he have for these assertions? Does the evidence from the last one-and-a-half centuries of a changing climate support them?

It is easy to claim "climate change" will cause more extreme weather events, but the evidence for this is somewhat lacking, as is any explanation as to why an increase in average world temperatures of just one or two degrees should be expected to have such disastrous consequences.

Carbon dioxide is not, as some seem to think, a pollutant - it is necessary for life on this planet; and one of the consequences of more carbon dioxide in the atmosphere is a greening of parts of the planet.

HC, Devon



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