When are extreme events part of natural climate variability and when are they due to climate change? It’s important to ask—no matter where you stand on the role of humanity’s impact on the environment.

A group of international scientists decided to address this question, focusing on a dozen or so extreme events from 2012. Their results were published last week in the Bulletin of the American Meteorological Society. (The findings are also available in a downloadable report.)

And the results, were, well, variable.

The researchers did not look at Hurricane Sandy, but they did examine the flooding and the inundation it caused. Because of sea-level rise (a direct result of climate change), the researchers determined that the superstorm did far greater damage than it would have with oceans at normal levels.

The team also determined that heavy rains in the United Kingdom, Japan, and China were not due to global warming, and Australia’s above-average rainfall was due to a La Niña event (or short-term climate variability).

However, a deluge in New Zealand was due to climate change. From Wired:

Total moisture available for this extreme event was 1% to 5% higher as a result of anthropogenic greenhouse gas emissions.

And Arctic sea ice melt? The cap of sea ice covering the North Pole shrunk to its smallest extent last summer. The cause? Climate change.

What about last year’s devastating drought in the Midwest? Scientists judged that climate variability was to blame—not global warming.

However, Stanford researchers did find that the extreme heat that came with last summer’s drought could be attributed to climate change. They also found strong evidence that the high levels of greenhouse gases now in the atmosphere have increased the likelihood of severe heat.

In addition, their findings indicate that extreme weather in the north-central and northeastern United States is more than four times as likely to occur than it was in the pre-industrial era.

The Palo Alto scientists hope the results from these studies can help to quantify the true cost of emissions to society, since the cost of the disaster is measurable.

“Knowing how much our emissions have changed the likelihood of this kind of severe heat event can help us to minimize the impacts of the next heat wave, and to determine the value of avoiding further changes in climate,” says lead author Noah Diffenbaugh, a Stanford associate professor of environmental Earth system science.

Image: Theresa L Wysocki/Flickr

Four amazing and passionate scientists discussed different aspects of our changing world—wildlife, drought, storms and the tree-ring record—at a press conference titled, “Did Climate Change Cause Superstorm Sandy?”

Remember, these are scientists, not politicians (see more in Andy Revkin’s New York Times blog). They need evidence to see causal effect between one event and another. And for these recent storms and weather patterns, there just isn’t enough evidence. Yet.

But are these researchers glad that these events are focusing Americans’ attention (including the President in his recent State of the Union address) on climate change? Most definitely. Yes.

Here’s what they do know. Climate change is affecting the probability of storms like Sandy and Nemo. There is evidence that in our warming world, severe storms will happen more frequently.

Researchers understand that global warming and other human-related activities are affecting where animals live, move and mate, and when plants bloom.

Scientists also know that temperature increase is one factor in drought. Texas temperatures have risen steeply in just the past 15 years and drought has increased.  And now Texans are talking about climate change, said John Nielsen-Gammon of Texas A&M University. The drought alone didn’t alarm them about climate change, but the decreased water supply has made people and politicians alike take notice.

And the speakers are hopeful and passionate that we’ll start doing something about these effects—reducing fuel emissions, restoring habitats, becoming more aware of climate change.

What do you know and feel? Share with us here.

Midwest drought image: cwwycoff1/Wikipedia

Weather on Uranus

Twenty-six years ago, when Voyager 2 took this image of Uranus, scientists were disappointed by the seemingly smooth surface of the distant planet. But earlier this week, astronomers displayed a wholly different picture (see right) of Uranus—sultry and stormy!

It took the Earth-based Keck Observatory to capture what Voyager 2 couldn’t, despite being only 50,000 miles from Uranus in 1986. Keck took sharp, high-resolution infrared images showing bizarre weather on the sideways planet.

The planet’s deep blue-green atmosphere is thick with hydrogen, helium and methane. Winds blow mainly east to west at speeds up to 560 miles per hour, in spite of the small amounts of energy available to drive them.

Scientists believe that the primary driving mechanism for these storms must be solar energy because there is no detectable internal energy source. “But the Sun is 900 times weaker there than on Earth because it is 30 times further from the Sun, so you don’t have the same intensity of solar energy driving the system,” says planetary scientist Larry Sromovsky. That might explain why storms on Uranus are much less violent than those on Earth.

Sromovsky and colleagues announced their findings this week at a meeting of the American Astronomical Society’s Division of Planetary Sciences.

What were you thinking?

That’s what we would like to ask local Russ George. This week, several news outlets report how George dumped 100 tons of iron into the Pacific Ocean off the British Columbia coast illegally.

George has a history of geoengineering attempts like this one. This time a native Canadian group hired him to reduce carbon in the ocean to boost dwindling salmon populations. If you recall from a story we ran last summer about this technique, iron can feed algal blooms, which then sink to the ocean floor, sequestering carbon as they do.

But tampering with the ocean like this is obviously dangerous and highly regulated. According to the New York Times, George dumped ten times as much iron as the experiment mentioned in our story and violated two international agreements on geoengineering.

Tigers, Detroit and otherwise

Even before Detroit finished New York off in the American League Championship Series on Thursday, talks of trading Yankee star Alex Rodriguez were rampant.

His post-season performance was so bad, he was benched for the last two games. And we all know how much the Yanks like to win. But A-Rod’s contract looks to be a losing proposition for the team—even if they are able to unload him, they’ll likely have to pick-up part of his remaining salary. Which is huge, according to ESPN,

Rodriguez, who will turn 38 next July, is signed for the next five years and guaranteed another $114 million.

In addition, his contract includes a marketing agreement with the Yankees that could add as much as $30 million to the deal…

Such a waste. If you’ll remember, a couple of years ago we discussed how his large salary could help save wild tigers. Who could use his help right about now. The Guardian reports that an Indian court lifted a ban on tourism in tiger reserves this week. Officials are hoping tourists and the tiger habitats can co-exist. Hopefully they have more luck co-existing than A-Rod and the Yankees.

Image: Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater

El Niño and La Niña both depend on ocean temperatures in the Pacific. The equatorial Pacific, specifically. If the temperatures are warmer than normal (based on averages from 1971-2000), that predicts a wet and warm El Niño pattern. If the temps are cooler, that means a colder, dryer La Niña is on its way.

And how is ocean temperature measured? By a satellite, of course. NASA’s Jason-2 satellite, where this image comes from, doesn’t measure temperature exactly, but measures sea surface height. Sea surface height is affected by both gravity and ocean circulation. Because gravity changes very little, the fluctuations in sea surface height are caused primarily by ocean circulation. The changing of the seasons, wind, warming and cooling all affect the circulation and therefore affect the height. According to NASA/JPL, “Using theory of ocean dynamics… sea-surface heights can be used to calculate how much heat is stored in the ocean below.”

Back to the image! The dark blue area in the center depicts the recent appearance of cold water hugging the equator, which the satellite measures as a region of lower-than-normal surface sea height. Voila La Niña.

“The next few months will reveal if the current cooling trend will eventually evolve into a long-lasting La Niña situation,” according to JPL oceanographer and climatologist Bill Patzert, PhD.

And that could be bad news for drought conditions in California and elsewhere. “For the American Southwest, La Niñas usually bring a dry winter, not good news for a region that has experienced normal rain and snowpack only once in the past five winters,” said Patzert.