As far as I can see there is overwhelming evidence that global warming is real, rapid and at the very least partly driven by human activities. Everything from plant hardiness zones moving north, melting sea ice, collapse of ice shelves, extremely rapid melting of glaciers and ice sheets, ecosystems moving towards the poles or to higher altitudes, and so on. In the past the speed of warming seems to have been underestimated – probably because of inadequate accounting for assorted positive feedback loops (eg warming causes permafrost to melt, releasing CO2 and methane, which in turn speeds warming, thereby making the rate of melting even faster.)
From the IPCC (Intergovernmental Panel on Climate Change) 2007 Assessment summary: “During the past 50 years, the sum of solar and volcanic forcings would likely have produced cooling. Observed patterns of warming and their changes are simulated only by models that include anthropogenic (us) forcings. IPCC is a real, credible, science based organization – not a bunch of hacks for sale to the highest bidder! It’s conclusions are based on peer reviewed results from a wide range of related disciplines. In fact, it’s just this wide range of data sources that makes their results so credible.
Look at greenhouse gases. Again from IPCC, “Atmospheric concentrations of CO2 (379ppm) and CH4 (1774ppb) in 2005 exceed by far the natural range over the last 650,000 years.” That’s a very powerful piece of data! I’m not a climate scientist but I do have a background in subjects such as thermodynamics and heat transfer. Maybe sunspots or other mechanism are at work in warming but I can assure you that CO2 and CH4 really are greenhouse gases (basic physics). They will have at least some warming effect – and with those numbers you are going to have a hard time convincing me that their effect won’t be significant.
Climate vs weather
There’s a big difference between predicting weather and predicting climate. To predict weather you need to analyze the effect of all kinds of forces that are varying all over the world while at the same time interacting and changing rapidly with time. The nature of the governing equations is such that the results are extremely dependent on initial conditions (chaos in the mathematical sense). Therefore, no matter how powerful your computers get you still won’t be able to predict complex weather more than a few days into the future.
Where weather prediction looks at the details, climate projections look at the big picture: basically they do an energy balance for the earth (energy in – energy out = energy gain). This still a VERY complex problem – energy flows and the earth’s response are not easy to quantify with a high degree of accuracy. However, you’re looking at the big picture, averages, long term trends – not whether the sun will shine on your house tomorrow – and the weather predictability limit of extreme dependence on initial conditions is not a factor.
Nothing is guaranteed
Predicting the future has its risks – there’s always the possibility of a black swan event that would shift the direction form global warming to cooling. Massive volcanic eruptions or a collision with an asteroid could send up enough dust to do it. Then there’s always the possibility of nuclear winter…..
Who do you believe
There is a solid consensus among climate scientists and people in related disciplines that global warming is occurring and that human activities are a significant cause. These people do not get their income by producing the results someone with funds is looking for. In general, support is going to go to people who get their work published in peer reviewed journals. Now I will be the first to agree that in science and science publishing there tends to be a bias towards work that fits in with generally accepted theories. However, this is just a bias, and good solid work that is outside of the mainstream will get through sooner or later. In this case the consistency of data from so many different sources has convinced me that this kind of bias is not a significant problem. An extensive review of the climate change skeptics side is here.
While there are real scientists on the denier side, most of what I’ve come across is disinformation and deliberate lies paid for by assorted corporate energy interests. To illustrate: James Hansen, a rather outspoken climatologist, was sort of a Paul Revere of global warming. His early work on the subject showed projections that were pretty accurate. He became a target for attacks (apparently funded by various energy interests) that attempted to discredit his work by any available means – including deliberate distortion. To this end Patrick Michaels, in Senate testimony and various presentations, showed a chart from a Hansen paper; only the chart had been modified to make Hansen’s projections look too high by creatively erasing part of it. The story, as determined by Paul Krugman of the NY Times, is here. Some background on Michaels is here.
Hansen has been criticized by some legitimate scientists. Data always is subject to interpretation and Hansen may have a tendency to reach a more dismal conclusion on a projection than other qualified scientists – but that’s a matter of data interpretation, not data falsifying! What probably gets him into the most trouble is his activism. Hansen is convinced that very bad things are happening to our planet, things that need to be stopped before it’s too late, and so he has plunged into the public and political arena. His activism doesn’t sit well with some of his colleagues. But given what he believes science is telling us isn’t his activism the proper moral choice? More details on Hansen are here.
Another example: A while back I received a fat envelope in the mail. Among other things, it contained a very nicely printed, glossy12 page reprint of an article from the Journal of American Physicians and Surgeons titled “Environmental Effects of Increased Atmospheric Carbon Dioxide.” The purpose of this mailing was to get me to sign an anti global warming petition. This letter apparently was sent to people with technical backgrounds in fields other than climate studies. They must have been a rather extensive mailing – I got two copies. Somebody spent a lot of money on it….
Papers published in obscure journals from totally unrelated fields simply are not believable. I didn’t investigate the report’s claims but others have. Check here and here for more. The more you look, the more you see a collection of people and organizations with highly questionable motivation and little if any scientific background in relevant fields.
From Wikipedia: “A climate tipping point is a point when global climate changes from one stable state to another stable state, in a similar manner to a wine glass tipping over.” Whether this is a useful or meaningful concept is debatable. However, it is pretty clear that global warming has had and will continue to have irreversible effects on planet earth.
Excessive greenhouse gas emissions will continue for years because it would take a really dramatic (and definitely traumatic) effort to make a significant difference. Cap and Trade is just a gift to Wall Street – it’ll do a lot more for Goldman Sachs than for climate. Realistically, the likelihood of major reductions in carbon emissions anytime soon is negligible. From the 2009 BP Statistical Review: for 2008, oil down 0.6%, natural gas up 2.5%, coal – the fastest growing for the last 6 years – up 3.1%. Coal being the growth fuel makes this particularly disturbing. From mining to burning there’s no such thing as clean coal and carbon capture and storage as a real mitigating technology is a long way off. Furthermore, even if we stopped adding carbon to the atmosphere, the CO2 we’ve already sent there is not going to come back down for many years to come.
Predicting the effect of climate change – who wins, who loses – is more difficult than predicting the climate change itself so there is a great deal of uncertainty in trying to assess the effects. Certainly, the movement of climate zones towards the pole and towards higher altitude is happening much too rapidly for ecosystems to adapt without severe damage. Warming, in combination with human activities such as industrial agriculture and rain forest clearing (which themselves contribute directly to warming), certainly will continue to result in major species extinctions – another “great dying”.