These are my (fairly) quick, rough, responses to the arguments and claim of Global Warming skeptics or deniers, or what you and me might otherwise consider common-sense objections to what is perceived to be the “blue sky theorising” of climate scientisists and global warming theorists.
1) “It’s been the coldest winter for so and so many years, where’s the global warming?” – Me: Global Warming refers to climate changes, not weather as such. Weather and climate are two different things; weather is short-term, climate is long-term.
2) “Weather forecasts can’t even be known a week in advance, why should I believe in climate models that claim to predict 100 years in advance?”. Me: This is related to #1, but with some additions. First, weather can be fairly accurately predicted in a timeframe of a few days, but over 5 days it becomes difficult to make accurate prognoses, and over 10 days, essentially impossible (though it is a question of the quality of your sensor data and how much computing power your are willing to expend to get your predictions). As for predicting the climate decades or even a century into the future, keep in mind that these ‘predictions’ aren’t really such – there are a great number of models based on various scenarios and assumptions for population, economic, climate mechanic etc. – for the exact reason that the climate scientists know they’re dealign with an extremely complex system with many “dials to adjust” so to speak. Climate science isn’t an entirely mature science yet, and while the field has in the past given sometimes erroneous or exaggered predictions, it is constantly changign and improving as observations are included into models and build on previous assumptions.
3) “Past predictions were wrong” or “it’s much colder these years than they predicted in the 1990′s”. Me: Several rebuttals to this kind of argument, which is also related to #2. a) Climate science isn’t exact, much as most science dealing in macro phenomena today isn’t. Most science operating on major, complex systems don’t make ‘predictions’ – they typically give a statistical chance of something happening, based on known initial conditions and the models these calculate from. b) You can’t dismiss the science because it can’t give you micrometer perfect data to compare up against. Skeptics should in this regard ask themselves how precise matches they want before they will accept the science/models as if not valid, then good enough to be trustworthy. Compare to my example: Would you also dismiss weather forecasting if it said that the temperatur tomorrow in your town was 12 Degrees C, and the thermometor outside your kitchen window showed 14 C? (or 13. or 12,5. or 12,1 – at which precision are you content?). Does climate science have to score a bullseye all the time for you to accept it? c) Also see next point.
4) “Warming stopped in 1997″. Me: This claim is based on data series using 1997 or 1998 as the basis year to compare against. Why is 1997 so significant? Because there is a massive ocean phenomenon called “El Niño” going on in the Pacific Ocean roughly every 7 years, which happened to coincide with that year. Not only that, it was a particularly strong example of the phenomenon. You then ask how some water current in a far away ocean should skew the temperatures so much? Keep in mind that The Pacific Ocean isn’t some village pond – it’s the planets greatest ocean, and the breadth of El Nino is from Australia to Equador – approximately 1/4 the circumference of the Earth. – Using 1997 as the base year for plotting the temperature developments globally would then make it seem like the global warming either slowed, stopped, or even reversed, depending on how agressively you cook the data. Fact of the matter is that, no, the warming has not stopped or reversed since 1997, however! it is true that it seemed to slow between 1997 and 2007, but true to the long-term trend, set new records again in 2009. Global warming has not stopped, and besides, no-one claims that it chugs along at a fixed, unchanging rate.
5) “Warming slowed the last couple of years, it must be showing that global warming is coming to an end”. Me: No. Short-term observations cannot reliably be used to make long-term prognoses. An everyday example I can offer is that because you had a fair bit of cash left over this month from after taxes, rent and food expenses are paid (as opposed to “normal” months where your personal finances ar ejust about break-even), doesn’t mean that you’re a millionaire a year from now.
6) “Surface temperature records are useless due to the Urban Heat Island effect, and thus cannot be used to show global warming”. Me: The UHI distortions are relatively minor, and second, despite the alleged major distortions of the UHI, the land station records show the essentially exact same global rise in temperatures as what is measured from satellite monitoring of the atmosphere.
7) “Artic Ice meltoff is negligible, as the 2007 drop is reversed, and the Ice coverage is back to normal”. Me: Yes, the *area* is not so far from the normal (recent recorded figures), but the *volume* isn’t. The speed of Ice meltoff depends on ice volume, not ice surface area. A solid block of 1 cubic metre of ice will of course take much longer to melt off than a slab of ice 1 square metre on the side, but otherwise 1 centimetre thick. (Try it yourself with varying sizes of ice cubes in your soft drink). Relevant to the point, the estimated volume of ice (multi-year ice) is at an all time low for the recording period.
“All the planets in the solar system are warming, so humans obviously can’t be causing Earthly warming”. Me: This claim is negated by that direct readings of the sun (solar output, insolation) shows little or no correlation with the warming observed both here on Earth, or on other planets (which by the way, have quite complex weather/climate systems of their own).
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I’ll add and update points as I think of them and as time allows. Thanks for reading.
Oh, and for further reading, I highly recommend John Cook’s site Skeptical Science, no matter what your persuasion or extent of knowledge of the global warming phenomenon, especially as it treats these points and many others in a very thorough and accessible fashion.
