- Climate Progress » Blog Archive » World carbon dioxide levels jump 2.3 ppm in 2008 to highest in 650,000 — if not 20 million — years: "A study in Science from the Global Carbon Project (see “More on soaring carbon concentrations“) noted: The present concentration is the highest during the last 650,000 years and probably during the last 20 million years. Worse, the rate of growth of CO2 concentrations this decade is 2.1 ppm a year — 40% higher than the rate from the 1990s. At the same time that CO2 emissions are soaring, CO2 sinks are saturating (see “The ocean is absorbing less carbon dioxide“)."
- Question of the day Gristmill: The environmental news blog Grist;
- Four Scary Surprises of Global Warming EcoGeek - Clean Technology;
- Open Left:: USGS Report: "Thresholds of Climate Change in Ecosystems":
" You've got a kettle on the stove. It sits atop the flame for several minutes as if the flame were not there. Then, all of the sudden, it starts whisltling. All of a sudden, liquid water is being turned into steam at a furious pace. A threshold has been crossed. There are thresholds in ecosystems, too. Points at which slight changes, which have previously had no noticeable effect, suddenly have a dramatic effect. And with ecosystems, sometimes the changes are irreversible. You can't just turn off the flame and have kettle stop boiling. The new state takes on a life of its own. Think of an ecosystem instead of a kettle and global warming instead of a flame, and you're got the subject of a new report from the US Geological Survey (USGS), "Thresholds of Climate Change in Ecosystems"." [...]
In a press release, the USGS explained: Slight changes in climate may trigger major abrupt ecosystem responses that are not easily reversible. [...]
An ecological threshold is the point at which there is an abrupt change in an ecosystem that produces large, persistent and potentially irreversible changes. "One of our biggest concerns is that once an ecological threshold is crossed, the ecosystem in question will most likely not return to its previous state," said USGS Associate Director for Biology Susan Haseltine. "The existence of thresholds should be a key concern of scientists and natural resource managers." The team also emphasized that human actions may increase an ecosystem's potential for crossing ecological thresholds. [...]
Ecological thresholds occur when external factors, positive feedbacks, or nonlinear instabilities in a system cause changes to propagate in a domino-like fashion that is potentially irreversible. Once an ecological threshold is crossed, the ecosystem in question is not likely to return to its previous state. Over the past three decades, climate change has become a recognized driver of ecosystem change. [...]
In addition to the gradual types of climate-related change mentioned above, there is increasing recognition that small changes in climate can trigger major, abrupt responses in ecosystems when a threshold is crossed. The potential for sudden, unanticipated shifts in ecosystem dynamics make resource planning, preparation, and management intensely difficult. These sudden changes to ecosystems and the goods and services they provide are not well understood, but they are extremely important if natural resource managers are to succeed in developing adaptation strategies in a changing world. [...]
There are numerous examples of sudden ecological change that fit the current qualitative definition of an ecological threshold and that were likely caused by climatic changes such as warming temperatures.
A clear example comes from recent observations of the Arctic tundra, where the effects of warmer temperatures have included reduced snow cover duration, which leads to reduced reflectivity of the surface. Reduced reflectivity causes greater absorption of solar energy, resulting in local warming, which, in turn, further accelerates the loss of snow cover. This amplified, positive feedback effect quickly leads to warmer conditions that foster the invasion of shrubs into the tundra. The new shrubs themselves then further reduce albedo and add to the local warming. The net result is a relatively sudden, domino-like chain of events that result in conversion of the arctic tundra to shrubland, triggered by a relatively slight increase in temperature....
Warming has caused a number of effects, including earlier snowmelt in the spring, reductions in sea-ice coverage, warming of permafrost, and resultant impacts to ecosystems including dramatic changes to wetlands, tundra, fisheries, and forests, including increases in the frequency and spatial extent of insect outbreaks and wildfire.
During the 1990s, south-central Alaska experienced the largest outbreak of spruce bark beetles in the world. Milder winters and warmer temperatures increased the over-winter survival of the spruce bark beetle and allowed the bark beetle to complete its life cycle in 1 year instead of the normal 2 years. Added to this were 9 years of drought stress, which resulted in spruce trees that were too weak to fight off the beetle infestation. For these forests, multiple climate-triggered stresses amplified each others' effects to cause a profound ecosystem change. The Alaskan spruce bark beetle outbreak and consequent forest die-off are an example of an actual climate-induced threshold crossing. [...]
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[...] See, global warming's not that bad. We're a whole lot smarter about it, once you get past the wingnuts."
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