According to two new climate reports, 2012 has been confirmed as one of the top 10 hottest years on record, globally, and the blame for the continued warming trend is placed squarely on the shoulders of humanity.
NOAA's National Climate Data Center (NCDC) issued their 2012 State of the Climate report yesterday, putting 2012 in the top ten of the hottest years on record (and hottest year on record for the United States and Argentina). The report notes the continuing rise in temperatures over both land and ocean, with rising trends starting as far back as the mid-19th century, a rise in humidity levels over the past 40 years (consistent with what is expected as air temperatures rise), and record or near-record level rises in sea level and ocean heat content.
It also noted declines in the climate as well, specifically with the depth and extent of the world's glaciers, with record or near-record lows in the temperature of the lower stratosphere (the layer of the atmosphere directly above where our weather happens), and record or near-record lows in the amount of sea ice observed, the depth and extent of the Greenland Ice Sheet, and the amount of snow cover seen.
With this being a fairly technical report, the NCDC doesn't make any hard-line comments beyond the science, the observations and the trends seen, but Kathryn D. Sullivan, Ph.D., the acting NOAA Administrator, said this in a statement:
"Many of the events that made 2012 such an interesting year are part of the long-term trends we see in a changing and varying climate — carbon levels are climbing, sea levels are rising, Arctic sea ice is melting, and our planet as a whole is becoming a warmer place. This annual report is well-researched, well-respected, and well-used; it is a superb example of the timely, actionable climate information that people need from NOAA to help prepare for extremes in our ever-changing environment."
At the same time, though, the American Geophysical Union (AGU) released their own report, titled Human-induced climate change requires urgent action. This is a fairly light-weight statement (2 pages, compared to the 258-page NCDC report), but it carries a heavy message:
"Human activities are changing Earth’s climate. At the global level, atmospheric concentrations of carbon dioxide and other heat-trapping greenhouse gases have increased sharply since the Industrial Revolution. Fossil fuel burning dominates this increase. Human-caused increases in greenhouse gases are responsible for most of the observed global average surface warming of roughly 0.8°C (1.5°F) over the past 140 years. Because natural processes cannot quickly remove some of these gases (notably carbon dioxide) from the atmosphere, our past, present, and future emissions will influence the climate system for millennia."
This new AGU statement is an update from their release in February 2012, where they had said that the evidence for our impact on the climate was strong, but this update makes it much more clear.
"AGU has a responsibility to help policy makers and the public understand the impacts our science can have on public health and safety, economic stability and growth, and national security," Gerald North, the chair of the AGU Climate Change Position Statement Review Panel, said in a statement. "Because our understanding of climate change and its impacts on the world around us has advanced so significantly in the last few years, it was vitally important that AGU update its position statement. The new statement is more reflective of the current state of scientific knowledge. It also calls greater attention to the specific societal impacts we face and actions that can diminish the threat."
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There are, and will still be, arguments against these statements.
There are claims that global warming and climate change have stopped since 1998. That's wrong. The original article that claimed that was thoroughly debunked by the very office that issued the information that article tried to use. There have been variations over the past 15 years or so, due to things like the shifting El Nino/La Nina patterns in the Pacific Ocean and suppression due to ash from volcanic eruptions, but these have only slowed the rise in temperatures. The rising trend is still there, and if you remove the influences of these effects, that is quite clear.
There are claims that the climate change we're seeing is due to the sun. That is also wrong. The amount of energy we've been receiving from the sun has declined, ever-so-slightly, since 1979. Also, if global warming was due to the sun, all layers of the atmosphere would see an increase in temperature. While temperatures in the troposphere (the lowest level of the atmosphere) are increasing, we are seeing a marked decrease in the temperature of the lower stratosphere (the layer directly above the troposphere).
Some respond to the claim about the record loss of Arctic sea ice by mentioning the record-setting extend of sea ice around Antarctica at roughly the same time. However the record high in sea ice extent near the south pole, which occurred during their winter, is due to immense amounts of fresh water pouring into the ocean there as it melts off the Antarctic ice sheets. In the Arctic, at least for the moment, we still have at least some sea ice left, even at the peak of the summer melt. In the Antarctic, all sea ice completely melts away during their summer peak, so it results in a net loss of ice from the south pole.
On the other side, there are some that have been saying it's too late. It's too expensive to do anything, and anything we could do wouldn't have much of an effect anyway. We've already had remarkable successes in other environmental campaigns, though, in reducing acid rain, ozone depletion and air pollution. We did it by coming together, recognizing what we're seeing and the dire effects if we ignore the problem, and doing something about it. It's not going to be easy to fix the problems we have now, but they couldn't be more important for our future, and they may even undo the successes we've had.
Climate change threatens to disrupt our ability to feed ourselves. It threatens our supply of drinking water. It spreads infectious diseases. It is even being linked to increased violence and conflict. It might be difficult and expensive to fix climate change, but the amount of work and the cost we'll pay to fix it now is tiny compared to the hardships and expenses that we are expected to endure if we do nothing.
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