Last week, the heaviest snowfall since the '90s blanketed the U.K., disrupting bus, rail and air transportation and costing areas like London a cool billion in lost revenue.

Meanwhile, in Australia, a punishing, record drought was worsened by the nation's worst heat wave and worst wildfires, wherein over 400 conflagrations killed over 200 people (and counting), torched a thousand homes and renewed calls for a country with its environmental head up its ass to finally launch its still-hibernating national warning system.

Those who would argue that these are isolated events do so at their own peril. The more time passes, the more both examples of extreme weather resemble two sides of the same fearsome coin known as catastrophic climate change.

And depending on how the science plays out, it could get much worse indeed, and fast.

Deniers of catastrophic climate change have been clinging to extreme rainstorms and snowstorms, such as those recently witnessed in the U.K. or American East Coast, like life rafts off the Titanic.

They still argue that such record-breaking deep freezes disprove global warming. But they're desperately seeking semantics, while the rest of the world is waking up to reality. Which is this: Catastrophic climate change will feature as much ice as fire. It probably already has.

"Scientifically, it would not be correct to make the statement that the current weather in Australia, the U.K. and U.S. are examples of climate change," explains Jian Liu, chief of the Division of Environment Policy Implementation's climate change adaptation unit at the United Nations Environmental Program. "Rather, these are extreme climate events; whereas climate change is something that can only be observed by looking at the average conditions over long periods of time. But while the general average trend is one of a warming climate, this does not mean that extreme cold events or snowstorms will not take place.

"In fact, as you rightly point out, climate change may even contribute to an increasing intensity of snowstorms, as moisture levels in the atmosphere rise."

Liu's point is a good one: It's only climate change, scientifically speaking, once you've had hundreds, or hundreds of thousands, of years to chart the differences and gradations in weather, extreme and otherwise. But we don't have hundreds of thousands of years to wait for that data to come through, which is probably why few scientists ever run for public office, where life-and-death decisions are made in advance of the data, often to influence it.

But disciplinary differences aside, this much is certain: Extreme weather has taken hold of our planet, the only one in our known universe capable of sustaining lives and habitats like ours, and we don't have hundreds of thousands of years to get our act together to forestall even worse
events, ones that are exponentially taking many lethal forms.

"Numerous long-term changes in the climate have been observed, including extreme weather such as droughts, heavy precipitation, floods, heat waves and increasing intensity of tropical cyclones," Liu says. "Trends towards more powerful storms and hotter, longer dry periods have been observed. As a result of reduced precipitation and increased evaporation, water-security problems are projected to intensify by 2030 in some regions, and significant loss of biodiversity is projected to occur by 2020 in some ecologically rich sites.

"As to your question on winter storms and cold events, those pointing at intense winter storms or extreme cold events as evidence that global warning is not happening are confusing weather and climate."

That arguably deliberate confusion has slowed our response to a danger that is snowballing by the day, but may disappear if some of climate change's more unlikely, but terrifying, possibilities come to pass.

In one scenario that has taken by storm, pardon the pun, scientists and disaster-cinema stalwarts like director Roland Emmerich -- director of the enviro-horror blockbusters The Day After Tomorrow and 2009's 2012 -- excessive concentrations of carbon dioxide in the atmosphere shut down our oceans' thermohaline circulation and plunges regions of Earth into a miniature ice age. Which regions? Wait for it: The U.K. and the American East Coast.

This thesis has been treated like an environmental, and geopolitical, football by scientists and policymakers alike, who have yet to agree on the scientific data or even what the data is looking for. But everyone seems to agree that the possibility of such an extreme global event warrants vigorous study.

"The potentially severe consequences of such an event, even if very unlikely, argues for a strong research effort to develop the observations, understanding and models required to predict more confidently the future evolution of the Atlantic Meridional Overturning Circulation (AMOC), or thermohaline circulation (THC)," warns Thomas Delworth, a scientist at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., as well as the convening lead author of a chapter on THC recently released in a voluminous report on global warming from the U.S. Climate Change Science Program.

"Based on our synthesis of the research to date, it is very likely that the strength of the THC will decrease over the course of the 21st century in response to increasing greenhouse gases, with a best estimate decrease of 25-30 percent.

"However, our assessment was that a collapse of the THC in the 21st century has less than a 10 percent chance, based on the fact that none of the state-of-the-art climate models project such a collapse when subjected to our best estimates of future changes in greenhouse gases and other factors that influence climate. However, although our current understanding suggests that such an event is very unlikely, the potential consequences of such an event could be severe."

Of course, NOAA's best estimates are likely as solid as those of the Nobel Prize-winning Intergovernmental Panel on Climate Change, whose scary 2007 report is already, according to the World Wildlife Fund, woefully out of date. Everything is worsening beyond what Earth's greatest scientists have concluded in what Delworth might call their "state-of-the-art climate models," which is a nice way of saying that they missed the forest for the trees.

So if you think a collapse of the THC is out of bounds, you might want to think again, and perhaps consider moving to, ironically enough, warmer climes if you live in the U.K. or the U.S. East Coast.

"There are some important climate processes that have a significant effect on regional climate, but for which the climate change response is still poorly known," explains the U.N.'s Liu. "These include thermohaline circulation. The uncertainties surrounding this, however, are high. Some measurements have detected evidence of weakening, while others point to a warming North Atlantic, implying that circulation is not weakening, or if it is, it is not having a cooling effect, or other factors are overriding the cooling effect.

"The general view is that the shutdown of the thermohaline circulation is a low-probability event, but one that would have major consequences."

That general view is in stark contrast to that of Michael Schlesinger, a professor of atmospheric sciences at the University of Illinois, Urbana-Champaign, who in 2005 infamously declared that the "shutdown of the thermohaline circulation has been characterized as a high-consequence, low-probability event. Our analysis, including the uncertainties in the problem, indicates it is a high-consequence, high-probability event."

Whatever the scientific consensus, or disagreement, we can't wait hundreds of thousands of years to see if the U.K. and U.S.' bitter cold will turn into an ice age, even as the rest of the planet burns. We need to act now. Liu suggests we start with the obvious.

"There is substantial economic and technical potential for mitigating climate change by reducing greenhouse-gas emissions, as well as enhancing sinks," he says. "Quite a number of policies exist in countries, both developed and developing, which, if implemented, could lead to emission reductions and contribute to sustainable development. And there are various ways in which greenhouse-gas emissions can be reduced: Using and saving energy more efficiently, replacing nonrenewable with renewable sources of energy, capturing and sequestration of carbon-dioxide emissions, and enhancing the carbon-dioxide-sink function of forests."

But even that won't stop the pain. Liu adds:

"Even if the most stringent mitigation measures were put in place today, the impacts of climate change would still continue for centuries."