This weekend in DC, where I live, we had temperatures at almost seventy degrees with people out in shorts playing football; then by Tuesday it snowed. Last week LA had temperatures in the eighties, once seen only in the summer. Singular warm days or unusual variations don't prove that climate change is underway, of course, but they are consistent with the long term trends. 2011 was a record year for extreme weather events, with twelve of them costing a billion dollars or more. Nine out of the top ten warmest years on record have occurred since 2000, with the tenth being 1998. No one not blinded by a capitalist or religious ideology can deny the reality of global warming at this point. The evidence, and personal experience, are now just too strong.
Indeed, over the last two decades there is a pattern of scientific projections understating how bad things really are. Before industrialization the carbon level in the atmosphere - more or less it's natural state before human intervention - was about 280 parts per million. We are now at about 380 ppms, and while a decade ago scientists were hoping to stabilize carbon levels at 550 ppms, now even that looks optimistic. The problem is that once we hit about 480 ppms, feedback loops will set in that catapult us automatically to 800 or 1000 ppms, far beyond human capacity for adaptation.
Furthermore, the climate is a highly complex system, so destabilizing it will lead to feedback loops that magnify negative trends and will cause inherently unpredictable, system-disrupting shocks that result in nightmare scenarios. The only uncertainty is what those particular destabilizing events will be, not that they will occur.
One of these will be the release of massive amounts of methane into the atmosphere as arctic oceans and frozen tundra warm, especially in Siberia. As a greenhouse gas, methane is twenty times more destructive than carbon. Scientists in Russia were recently surprised to discover that massive plumes of it are already issuing from the undersea continental shelf off of the east Siberian Arctic Shelf, and those plumes are not small, according to Dr. Igor Semiletov of the International Arctic Research Centre at the University of Alaska Fairbanks:
"Earlier we found torch-like structures like this but they were only tens of metres in diameter. This is the first time that we've found continuous, powerful and impressive seeping structures more than 1,000 metres in diameter. It's amazing," Dr Semiletov said.
The consequences of even modest climate change, which will start feeling within a few decades, are horrendous for humans and other species: relatively rapid sea level rise and species migration to northern climes, causing major human migrations as well - and recall that it was much smaller migrations of Eurasian tribes that ultimately brought down Roman civilization and ushered in the Dark Ages (which some historians call the "Migration Period.") Food, water, and other resource scarcity as we deplete our hydrocarbons, tap out our fisheries, and turn good farmland into desert will lead to more and larger wars, including conflicts between future great powers armed with nuclear, chemical, biological, and other advanced weaponry. Mass extinctions of species, both plants and animals, are likely to occur. And triggering disruptive climate shocks will overwhelm us: global warming that melts the Greenland ice sheet could paradoxically trigger a new ice age, for example, meaning that we would experience several decades of warming followed by a decade or less of rapid cooling, a prospect that civilization is unequipped to handle. Genetics tells us that during the last ice age humanity shrunk to only a few thousand individuals and was barely able to pass on our genome. Another shock scenario is the rapid release of methane that leads to very rapid global warming in a few years, the pace of which would wipe out human civilization and most species, leaving the surface of the planet a mostly barren wasteland. Given the recent discoveries, has this scenario already begun?
A decent, democratic, technological civilization depends on a stable climate that does not change - maybe any kind of civilization at all does, even an agrarian one. Indeed, in the worst case, life itself on Earth depends on us preventing climate change, as "Venus scenario" could create a planet here that is as uninhabitable as Venus, with its atmosphere of carbon dioxide and constant acid rain.
Yet conservatives continue their denial. The reasons why don't actually matter, because those reasons are, bluntly put, abjectly insane. Global warming denial is a form of psychosis because those engaged in it do not see what is really there, and our psychological authorities should classify it as such and we should start excluding deniers from public office as we do schizophrenics. The scientific proof has been long established, and nothing else need be said except to repeat the above consequences as loudly and often as possible, and to defeat conservatism and drive deniers from positions of authority as rapidly as can be done.
I do think that we can avoid the worst of the effects of climate change if we come to our senses. A Stanford study released last year showed that the globe can adopt a sustainable energy system based on renewables by 2025 at a very modest cost to global GDP, and if we implement that and other mitigation strategies we at least can stop making climate change worse. One other mitigating factor would be to establish egalitarian economies, because consumption rather than population is the main contributor to our environmental problems, including climate change. Ending the decadent over-consumption of the global elite would be both a great social and environmental boon. And we probably must implement some type of geoengineering for several decades to cool the planet until we and future generations remove the excess carbon from the atmosphere. But much of the damage that we have set in motion is unavoidable - excess atmospheric carbon is currently acidifying the oceans, bleaching of the extremely life-rich coral reefs. We are probably going to lose all life in the oceans before this is over, destroying much of the richness and diversity of the Earth's biosphere. That will be a real geological tragedy, and future generations will be right to hold us in utter contempt for it - if we even get our act together in time to make sure there are future generations to remember what we've done.