That bold statement may seem like hyperbole, but there is now a very clear pattern in the scientific evidence documenting that the earth is warming, that warming is due largely to human activity, that warming is causing important changes in climate, and that rapid and potentially catastrophic changes in the near future are very possible. This pattern emerges not, as is so often suggested, simply from computer simulations, but from the weight and balance of the empirical evidence as well.
The great cryo-scientist Lonnie Thompson has a must-read paper, “Climate Change: The Evidence and Our Options.” Thompson has been the Paul Revere of glacier melt.
I wrote about his important 2008 work “Mass loss on Himalayan glacier endangers water resources” (see Another climate impact comes faster than predicted: Himalayan glaciers “decapitated”). It concluded ominously:
If Naimona’nyi is characteristic of other glaciers in the region, alpine glacier meltwater surpluses are likely to shrink much faster than currently predicted with substantial consequences for approximately half a billion people.
The study notes that Naimona’nyi is the highest glacier (6 kilometers above sea level) “documented to be losing mass annually.” MSNBC reported:
Lonnie Thompson of Ohio State University and a team of researchers traveled to central Himalayas in 2006 to study the Naimona’nyi glacier, expecting to find some melting”¦. But when the team analyzed samples of glacier, what they found stunned them”¦.
In fact, the glacier had melted so much that the exposed surface of the glacier dated to 1944″¦.
“At the highest elevations, we’re seeing something like an average of 0.3 degrees Centigrade warming per decade,” Thompson said”¦.
“I have not seen much as compelling as this to demonstrate how some glaciers are just being decapitated,” Shawn Marshall of the University of Calgary said”¦.
“You can think of glaciers kind of like water towers, “ he said. “They collect water from the monsoon in the wet season, and release it in the dry season. But how effective they are depends on how much water is in the towers.”
In his new paper, he joins the climate hawks and the legion of uncharacteristically blunt scientists. He explains something that is really understood only by those who read the scientific literature and/or talk to the leading climatologists — we are in big, big trouble:
Climatologists, like other scientists, tend to be a stolid group. We are not given to theatrical rantings about falling skies. Most of us are far more comfortable in our laboratories or gathering data in the field than we are giving interviews to journalists or speaking before Congressional committees. Why then are climatologists speaking out about the dangers of global warming? The answer is that virtually all of us are now convinced that global warming poses a clear and present danger to civilization.
And, as noted in the quote at the top, this isn’t just based on models of the future, but on observations and analysis of the past:
Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds of years to multiple millennia, suggesting that climatological conditions that dominate those regions today are different from those under which these ice fields originally accumulated and have been sustained. The current warming is therefore unusual when viewed from the millennial perspective provided by multiple lines of proxy evidence and the 160-year record of direct temperature measurements. Despite all this evidence, plus the well-documented continual increase in atmospheric greenhouse gas concentrations, societies have taken little action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions continues to accelerate. As a result of our inaction, we have three options: mitigation, adaptation, and suffering.
In that final sentence, Thompson picks up the formulation that science advisor John Holdren likes to use (see “Real adaptation is as politically tough as real mitigation, but much more expensive and not as effective in reducing future misery: Rhetorical adaptation, however, is a political winner. Too bad it means preventable suffering for billions”).
The paper does a good job of running through the science, and then discussing the key impacts, including the ones that don’t get enough attention:
Global warming is expanding arid areas of the Earth. Warming at the equator drives a climate system called the Hadley Cell. Warm, moist air rises from the equator, loses its moisture through rainfall, moves north and south, and then falls to the Earth at 30u north and south latitude, creating deserts and arid regions. There is evidence that over the last 20 years the Hadley Cell has expanded north and south by about 2u latitude, which may broaden the desert zones (Seidel, Fu, Randel, & Reichler, 2008; Seidel & Randel, 2007). If so, droughts may become more persistent in the American Southwest, the Mediterranean, Australia, South America, and Africa.
For more on that subject, see NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe and Must-read NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path.
Like any scientist familiar with the paleoclimate literature and recent observations, he is concerned with abrupt climate change:
So, not only is Earth’s temperature rising, but the rate of this change is accelerating. This means that our future may not be a steady, gradual change in the world’s climate, but an abrupt and devastating deterioration from which we cannot recover.
Abrupt Climate Change Possible
We know that very rapid change in climate is possible because it has occurred in the past….
One way that rapid climate change can occur is through positive feedback. In the physical sciences, positive feedback means that an event has an effect which, in turn, produces more of the initial event. The best way to understand this phenomenon as it relates to climate change is through some very plausible examples:
Higher global temperatures mean dryer forests in some areas, which means more forest fires, which means more CO2 and ash in the air, which raises global temperature, which means more forest fires, which means.”¦
Higher global temperatures mean melting ice, which exposes darker areas (dirt, rock, water) that reflect less solar energy than ice, which means higher global temperatures, which means more melting ice, which means”¦
Higher global temperatures mean tundra permafrost melts, releasing CO2 and methane from rotted organic material, which means higher global temperature, which means more permafrost melting, which means.”¦
Positive feedback increases the rate of change. Eventually a tipping point may be reached, after which it could be impossible to restore normal conditions. Think of a very large boulder rolling down a hill: When it first starts to move, we might stop it by pushing against it or wedging chocks under it or building a barrier, but once it has reached a certain velocity, there is no stopping it. We do not know if there is a tipping point for global warming, but the possibility cannot be dismissed, and it has ominous implications. Global warming is a very, very large boulder.
For more on feedbacks, see Science: Vast East Siberian Arctic Shelf methane stores destabilizing and venting: NSF issues world a wake-up call: “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.” And yes, I am familiar with the recent NASA work in this area and will be blogging on it this week.
Like any scientist who has endeavored to inform the public on this issue, he has run into the disinformation campaign:
Clearly mitigation is our best option, but so far most societies around the world, including the United States and the other largest emitters of greenhouse gases, have done little more than talk about the importance of mitigation. Many Americans do not even accept the reality of global warming. The fossil fuel industry has spent millions of dollars on a disinformation campaign to delude the public about the threat, and the campaign has been amazingly successful. (This effort is reminiscent of the tobacco industry’s effort to convince Americans that smoking poses no serious health hazards.)
But all the lies in the world — and the election of a slate of climate zombies in this country — can’t stop the reality of human-caused global warming. Only an aggressive effort to slow and then reverse greenhouse gas emissions trends can. Failure to do so would be immoral:
Unless large numbers of people take appropriate steps, including supporting governmental regulations aimed at reducing greenhouse gas emissions, our only options will be adaptation and suffering. And the longer we delay, the more unpleasant the adaptations and the greater the suffering will be.
Sooner or later, we will all deal with global warming. The only question is how much we will mitigate, adapt, and suffer.
Kudos to Thompson for not pulling any punches.
Here a nice video of Thompson and his wife explaining their work (h/t DotEarth):