Global Climate
Signs & Symptoms of Climate Change
1. Carbon Dioxide Concentrations in the Atmosphere Are Increasing
-By the time continuous monitoring began at Mauna Loa Observatory in
Hawaii, carbon dioxide particles had climbed above 310 parts per million (ppm)
and is now closing in on 400 ppm. Because we know that carbon dioxide is a
greenhouse gas, we can reasonably infer that increasing the amount of CO2 that
enters the atmosphere, particularly at the level of 90 million tons a day, will
increase the greenhouse properties of the atmosphere and thus lead to warming.
2. The Hottest Decade on Record Keeps Changing
-Whether measured from land or from satellite, it is clear that global temperatures are increasing. Averaged over all land and ocean surfaces, global mean temperatures have increased by approximately 1.33 degrees Fahrenheit (0.74 degrees Celsius) over the past century.
3. The Rate of Warming is Unprecedented in at Least 11,000 Years
-Of course, Earth's climate has historically undergone numerous significant shifts. It has been, at various times, both much warmer and much colder on average than it is now. How do we know that what is happening now is not one of those natural cycles? Well, for one thing, none of the natural forces - tilts in the planet's axis, wobbles in its orbit, or increased solar activity - are factors (the Sun, in fact, has been going through a slight cooling cycle even as temperatures on Earth have increased).
4. Arctic Sea Ice Is in a ‘Death Spiral’
-Because the thinner ice(first-year ice) forms each winter, it is more vulnerable to break-up and melt the following summer. The growing dominance of this thinner ice means that the volume of Arctic Ocean sea ice has also collapsed, from approximately 16,855 cubic kilometers in 1979 to roughly 3,261 cubic kilometers in 2012. In other words, Arctic sea ice has lost 80 percent of its volume. Some experts think we could see nearly ice-free summers in the Arctic Ocean in a decade if present trends continue.
5. Greenland Is Losing Ice at an Accelerating Rate
-How much ice is Greenland losing? At present, almost 300 gigatonnes per year - which, on the face of it, means we'd have to wait about 10,500 years until the ice sheet completely dissipated. But of course, the ice sheet will contribute significantly to sea level rise long before it disappears entirely. The rate of ice loss is increasing so rapidly that just ten years ago it was extrapolated that total ice sheet dissipation would happen in 22,000 years. And the rate of ice loss is still increasing.
6. Antarctica Peninsula Is Also Losing Ice at an Accelerating Rate
-Much of Antarctica is warming, but the Antarctic Peninsula - the region that reaches northward toward the tip of South America - is actually the most rapidly-warming part of the Southern Hemisphere, having seen temperatures increase by about 2.8 degrees Celsius over the last 50 years. Even when ice shelves don't collapse, their surfaces partially melt during summer - and according to new research, they are doing so now at a rate more than ten times greater than 600 years ago.
7. The Ocean Is Warming
-Inevitably, much of the climate attention focuses on the planet's surface - because that's the part where we live. But 90 percent of global warming goes into heating, not the land or atmosphere, but the ocean. Because it takes far more energy to heat up the entire ocean than the lower atmosphere or a surface layer of ice, the amount that the ocean has warmed is much less than on land: on average, about 0.025 degrees Celsius a decade - or slightly more than one-tenth of a degree Celsius over the last 50 years. Interestingly, this warming is not just affecting the surface of the sea; 30 percent of ocean warming has been taking place in waters deeper than 700 meters, and some has even occurred in the deepest, abyssal waters of the ocean.
8. Sea Level Is Rising
-This sudden shift in the Pacific “changed rainfall patterns all across the globe, bringing massive floods to places like Australia and the Amazon basin.” The water to power that rainfall came from the ocean, the level of which consequently dipped. Since then, sea level has resumed rising at an accelerated clip of approximately 10 mm a year. Researchers believe that, even as the overall trend will remain clearly upward, it may increasingly manifest in rapid short-term divergences - deeper potholes, such as that of 2010-11, and steeper speed bumps, such as the one we are witnessing now.
9. The Planet Is Accumulating More Heat
-Satellite measurements of incoming and outgoing radiation, as well as studies that have combined measurements for land, ice, atmosphere and the ocean have all shown one unmistakable fact: the planet is accumulating heat, and doing so at a growing rate. When you consider all the heat building up in the entirety of our climate, global warming has actually accelerated over the past 16 years that deniers claim nothing is happening. So the heat build-up continues unabated. Not only is global warming not slowing down, it is increasing. If and when that "hidden heat" returns to the atmosphere, the impact will likely be felt strongly.
10. Extreme Weather Is More… Extreme
-For example, a warming ocean, while actually making it more difficult for hurricanes to form, is leading to the hurricanes that do form to become stronger. When major storms do strike, higher sea levels will result in greater storm surges and coastal flooding. As the Arctic warms, circumpolar wind patterns are becoming disrupted, altering the course of the jet stream, which steers weather systems from west to east around the northern hemisphere. As a consequence, says a recent study, the jet stream is becoming “wavier,” with steeper troughs and higher ridges. Weather systems in turn are progressing more slowly, raising the chances for long-duration extreme events, like droughts, floods, extreme snowfall in winter, and heat waves. Recent studies have attributed some recent rainfall extremes to climate change, with a warmer atmosphere able to hold more moisture, while others indicate that many recent heat-waves would not have occurred without global warming. Weather events will always be subject to natural variability. But weather extremes are one predicted consequence of a changing climate, and the evidence is growing that recent examples of those extremes are not isolated, but rather harbingers of a new normal in a warming world.
