Q: “I am still confused about whether man-made global warming actually exists – how is it that there is still argument about interpretation of the facts (and even the facts themselves)?”
A: Some points to bear in mind:
1. Humans are (ecologically speaking) a ‘weed’ species, the toughest vertebate predator and coloniser that ever evolved.
2. Once we learned how to prevent or cure most infectious diseases, and how to use the energy in fossil fuels, an explosion in our numbers and impact became inevitable.
3. True to our nature, and now armed with numbers and machines, we have been aggressively burning, ploughing, ranching, trawling, mining, logging and polluting local ecosystems.
4. What is hard to see is that all these local ecosystems add up to a planetary ecosystem (the Biosphere, or Gaia), which as a whole is showing signs of stress (as indicated by oceanic dead zones, spreading deserts, declining wilderness forests and grasslands, collapsing fish stocks, falling water tables, rising concentrations of greenhouse gases, etc.). We are the first generations with access to knowledge about this huger, planet-wide context.
5. But seeing this big picture requires one to travel a lot with a trained eye, or read books by people who do. A ‘trained eye’ here means that of someone who pays attention to and can understand ecological signals – who can spot wind and water erosion or the difference between logged-over scrub and old-growth forest, who understands what NGO types are saying about declining wildlife populations or biodiversity, or who obsessively records things (the timing of Spring, the salt content of well-water, etc.). Not necessarily a professional life scientist or with formal training in these fields, but someone who ‘talks the talk’.
6. Even less obvious, however, are the subtleties of atmosphere, climate, weather and the interlinkages of atmospheric and oceanic chemistry and physics. These subjects can only be cracked by specialised, scientifically-trained professionals wielding serious kit and long-term, expensive research programmes, and these are only now beginning to yield a reliable, predictive understanding of these complex, turbulent systems.
7. A word about what science is. One definition: “The use of empirical observation and systematic description of phenomena to enrich critical, rational thought about them, and the pursuit of the logical consequences of those thoughts to make predictions that can then be tested through experiment”. By these means (and others, like the formality of peer reviewing publications) millions of scientists effectively cooperate in building an expanding, internally-consistent description of the world, against the Gold Standard of “a reliable, predictive understanding” of it.
8. But note that there is no such thing as ‘consensus’ among all scientists, since if there were, scientific progress would halt because it would be starved of original thinking. Instead there is ‘consilience’ over large areas where the evidence is so strong and everything fits together so well that for now (pending some change in perspective) interesting questions cannot be asked. This is where we are with the basic physics of the greenhouse effect.
9. Now the question posed is really, “how reliable is our understanding of man-made global warming?”. The official (IPCC) answer is that, taking into account all the knowledge that scientists have accumulated, and their interpretation of that knowledge, it is now virtually certain that people have caused an enhanced greenhouse effect which is now having and will continue to have a variety of impacts through the whole Biosphere, most immediately through climate and weather, sea-level rise and oceanic chemistry. Many informed people would leave out the ‘virtually’ and go directly for certainty.
10. However, there is much less official certainty over the precise locations, scales, speeds and impacts of changes that have already occurred or that are to be expected. Although the overall pattern is clear, on the details there is debate among observers and modellers, room for slightly different interpretations of data sets, and the usual scope for human error and foolishness. Even so, the official answer to the question of reliability implies that we are sure enough that many impacts will probably be severe, increasing and irreversible to justify major investments in capping or reducing atmospheric GHG concentrations.
11. After that, other questions arise about the investments needed, such as: “how major?”, “by whom?”, and “in what?” Whatever the answers, this is big money and involves big changes in industrial and economic policy, so things get complicated and political. Because any change implies that there may be winners and losers, some people feel threatened and organise themeselves to resist it. Resistance to combatting climate change goes back to the very moment when scientists started to be listened to by the media on the subject, and has been effective in delaying action for decades.
12. The opposition exploits scientific uncertainty (and occasional errors) over detailed events and predictions in order to cast doubt on the big picture, as a way to confuse the public and sap political will. Their aim is to head off frightening change, and to prolong business as usual (and the value of their investments in it) as long as possible. They make use of the fact that most people are not scientifically trained, and only a few thousand world wide are truly au fait with all the evidence, so the climate change story seems to rely on taking the word of “alarmist left-wing boffins” backed up on the streets by “green anarchists”. It’s an easy alliance to discredit.
13. So to conclude: allowing for how science works, and the specialised nature of some of the knowledge available, there is overwhelming evidence that people are having a whole range of destructive impacts on the Biosphere, including those that are both causes and consequences of climate change. It might be that we are already committed to a simplifed, hot Biosphere, or that we are simply unable to find leaders who can explain the science in popular terms, convince enough people of the need for action, and implement change fairly and effectively enough to do the job. Or, it might be that these conditions can still be fulfilled.