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

While the planet warmed steadily at a rate of 0.13° C per decade since 1950, since 1998 it’s been on a hiatus, despite the fact that levels of carbon dioxide, the main greenhouse gas produced by human activities, continued a steady rise, reaching 400 parts per million for the first time in human history in May 2013.

Two researchers from Scripps Institution of Oceanography at UC San Diego discovered the reason for this hiatus, publishing their findings last week in Nature.

The reason for the warming break? Cooling in the eastern tropical Pacific Ocean. The team predicts that long-term global warming will resume when the tropical Pacific switches back to a warm state.

The researchers arrived at their conclusion using innovative computer modeling methods to simulate regional patterns of climate anomalies. This enabled them to see global warming in greater spatial detail, revealing where it has been most intense and where there has been no warming or even cooling.

The current cooling phase began just after a strong El Niño year in 1998. The study considers the tropical Pacific Decadal Oscillation (PDO), a climate cycle that plays out over the course of several decades. Within this large pattern fall El Niño and La Niña, well-known faster cycles that cause shifts in the distribution of warm water in the equatorial Pacific Ocean. While El Niño and La Niña last only a few years, the PDO lasts several decades. The last time it was in a cooling phase—cooling waters in the eastern equatorial Pacific Ocean—it lasted from roughly 1940 to the early 1970s. The researchers are unsure how this long this phase will last.

“That speaks to the challenge in predicting climate for the next few years,” says study co-author Shang-Ping Xie.  “We don’t know precisely when we’re going to come out of [the hiatus] but we know that over the timescale of several decades, climate will continue to warm as we pump more greenhouse gases into the atmosphere.”

“These compelling new results provide a powerful illustration of how the remote eastern tropical Pacific guides the behavior of the global ocean-atmosphere system, in this case exhibiting a discernible influence on the recent hiatus in global warming,” says Dan Barrie, program manager at the NOAA Climate Program Office.

Image: Kosaka, Xie/Scripps

How will climate change affect different species? Will organisms be able to adapt quickly enough to survive in a rapidly changing environment?

Researchers at the University of Oxford are attempting to predict this with small, short-lived birds like the great tit (Parus major). In a study published this week in PLoS Biology, the scientists discovered that great tits living in a forest near Oxford have been able to survive and adapt to a 1°C temperature increase over the past 50 years.

After analyzing those 50-plus years of data collected on the birds in their habitats, the authors studied when the birds lay their eggs relative to spring temperatures, as well as how the birds have tracked the shifts in peak caterpillar numbers caused by the changes in temperature. They found that the birds are now laying their eggs an average of two weeks earlier than they did 50 years ago, primarily as a result of phenotypic plasticity.

Phenotypic plasticity enables organisms to adjust their behavior rapidly in response to short-term changes in the environment. Jack Dumbacher, curator and department chair of Ornithology & Mammalogy here at the Academy, explains, “It’s heritable but it’s not an evolutionary, or genotypic change. There’s no change in the genes.”

The authors’ predictions show that phenotypic plasticity could allow the great tits—and similar birds—to survive warming of 0.5°C per year, easily outpacing the current worst-case scenario of 0.03°C from climate models.

Dumbacher says that while this study is interesting and a good reminder how adaptable one species may be, he emphasizes that temperature increase is just one effect of climate change. Temperature variance and extreme weather are other effects with unknown results to various ecosystems, he says. In addition, Dumbacher reminds us that the great tits and caterpillars play roles in a much larger ecosystem, where the web of relationships is so interdependent that one small change to one small organism in that web could easily affect other species.

One effect of climate change that Dumbacher stresses (and the study does not mention) is invasive species. As temperatures change, habitat ranges change for different species, which can result in one species invading the habitat of another. One example Dumbacher gives is the Northern Spotted Owl (Strix occidentalis caurina). These birds have been able to adapt to a 1°C temperature increase over the past 100 years but are now facing a fierce competitor in the Barred Owl (Strix varia), an eastern species that now finds itself in the same territory as the Northern Spotted Owl.

“Climate change is more than a one degree temperature increase,” Jack says. “And while a species may demonstrate plasticity within different temperature regimes, it’s likely that ecosystems are not as adaptable. This why climatologists have such a difficult time predicting the effect of climate change on organisms.”

Image: Luc Viatour/Wikipedia

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

A recent article in PLoS ONE takes the naturalists’ records and compares plants’ blooming times from then to now—specifically 2012, with its record-breaking temperatures.

Not surprisingly, plants are blooming earlier. Previous research has demonstrated this, but not with specific places and plants.

Compared to the timing of spring flowering in Thoreau’s day (in the mid-1800s), native plants such as serviceberry and nodding trillium are blooming 11 days earlier, on average, in the area around Concord, Massachusetts, where Thoreau famously lived and worked.

Nearly a thousand miles away in Wisconsin, where Leopold gathered his records of blooming plants like wild geranium and marsh marigold, the change is even more striking. In 2012, the warmest spring on record for Wisconsin, plants bloomed on average nearly a month earlier than they did just 67 years earlier when Leopold made his last entry.

“We were amazed that wildflowers in Concord flowered almost a month earlier in 2012 than they did in Thoreau’s time or any other recent year,” says lead author Elizabeth Ellwood, “and it turns out the same phenomenon was happening in Wisconsin where Aldo Leopold was recording flowering times. Our data shows that plants keep shifting their flowering times ever earlier as the climate continues to warm.”

I asked Peter Fritsch, curator and chair of the Academy’s Botany Department, about the recent paper.  “The study makes clear that the strong link between increasing spring temperatures and earlier flowering times holds even during the hottest years known; other factors, such as unmet winter chilling requirements, appear not to have constrained or disrupted this link. Whether this link continues at even higher temperatures remains to be seen.

“Although this could mean that plants will be able to continue fairly normal patterns of reproduction, albeit at earlier and earlier times,” he adds, “other environmental factors, some of which could be critical to plant species’ survival, will likely be changing as well. For example, insect pollinator or seed disperser activity may become reduced or mistimed relative to flowering or fruit set.”

The new PLoS ONE study reminded me of the Grinnell Resurvey Project, where UC Berkeley scientists revisited locations documented by Joseph Grinnell a century ago. Grinnell thoroughly recorded fauna in several locations in California and modern-day researchers could document changes from his original observations. Peter says that he knows of no directly comparable studies in our area, that is, those that have looked at the changes in California flora and blooming time over such a long period of time.

Thoreau and Leopold (and Grinnell, for that matter) likely had no idea their records would prove to be so helpful in this particular way, decades later, Peter says. “This study also provides neat insight into one way that science works. In this case, I doubt very much whether it would have occurred to Thoreau that the notes he was recording on flowering times could be used for assessing long-term changes in climate. Yet, without his basic data and that from Leopold, the current study would not be nearly as conclusive.”

One last note from Peter: One of the co-authors on the study, Charles Davis, has Academy ties. He was a Summer Systematics Institute intern in the 1990s!

Yesterday, James Hansen of NASA’s Goddard Institute and Thomas Karl of NOAA’s National Climatic Data Center held a joint press conference, describing very similar findings for last year’s warmer than average temperatures around the world. A pdf with their organizations’ side-by-side comparisons is available here.

The average temperature globally in 2012 was about 58.3 degrees Fahrenheit, which is 1.0 F (0.6 C) warmer than the mid-20th century baseline. The average global temperature has increased about 1.4 degrees F (0.8 C) since 1880, according to the new analysis.

The scientists emphasized that weather patterns always will cause fluctuations in average temperature from year to year, but the continued increase in greenhouse gas levels in Earth’s atmosphere assures a long-term rise in global temperatures. Each successive year will not necessarily be warmer than the year before, but on the current course of greenhouse gas increases, scientists expect each successive decade to be warmer than the previous decade.

“The U.S. temperatures in the summer of 2012 are an example of a new trend of outlying seasonal extremes that are warmer than the hottest seasonal temperatures of the mid-20th century,” Hansen said. “The climate dice are now loaded. Some seasons still will be cooler than the long-term average, but the perceptive person should notice that the frequency of unusually warm extremes is increasing. It is the extremes that have the most impact on people and other life on the planet.”

In fact, according to Reuters, Americans are feeling the impact of climate change already—consequences that affect “health, infrastructure, water supply, agriculture and especially more frequent severe weather.”

But studies show we can do something about it. Nature Climate Change has an article this week describing how cutting emissions can reduce impacts from climate change. (Read more at Scientific American.) And New Scientist reports that while global talks breakdown over the subject, individual nations are doing something about it. Let’s hope the trend continues.

Want to engage more in the changing climate? Tomorrow Science will host a live chat, “Can We Conquer Climate Change?” Sign in here.

Image: NASA Goddard’s Scientific Visualization Studio

Another climate and water story

Last week, we featured a series of stories on climate change and water issues and this one slipped by. A study in Nature last week reported how trees physically respond to drought. And the news is not good. Plants undergoing drought stress experience reduced pressure in the xylem (the vessel that transports water from the soil to the leaves).

Head over to NPR to read (or listen to) their piece on the study.

Melting ice sheets and sea level rise

A NASA/ESA study, published in Science this week provides the most thorough representation of the rate of melting ice sheets and corresponding sea level rise to date. Using extensive satellite data, scientists report that the ice sheets covering Greenland and Antarctica are losing more than three times as much ice each year as they were in the 1990s. About two-thirds of the loss occurs from Greenland, with the rest from Antarctica.

Combined, melting of these ice sheets contributed 0.44 inches to global sea levels since 1992. This accounts for one-fifth of all sea level rise over the 20-year survey period. The remainder is caused by the thermal expansion of the warming ocean, melting of mountain glaciers and small Arctic ice caps, and groundwater mining.

“Both ice sheets appear to be losing more ice now than 20 years ago, but the pace of ice loss from Greenland is extraordinary, with nearly a five-fold increase since the mid-1990s,” NASA’s Erik Ivins says.

Ocean acidification and fighting back

Ocean acidification is already having an effect on marine life, according to a study published this week in Nature Geoscience. Shells of live mollusks from the Southern Ocean are showing signs of “severe dissolution.” New Scientist has more information.

Washington State is taking action to curb ocean acidification and protect the state’s large shellfish industry. A report, released this week, outlines plans to target pollution that causes acidification (including carbon emissions and agriculture run-off) and has a $3.3 million backing. More information is available here.

Maybe more coastal states (and nations) will follow Washington’s lead, says the Ocean Conservancy.

A Sad Factoid

A final thought from the editors at grist.org, who note that “if you’re 27 or younger, you’ve never experienced a colder-than-average month.” A truly sobering fact gleaned from the NOAA “State of the Climate” report for October 2012.

Image: Ian Joughin

For scientists, policy-makers and organizers who frequently discuss climate change, the last few years have been rough! While they still may be discussing it amongst themselves, with the economic downturn, a larger audience has been absent. An episode of Frontline explores the massive shift in public opinion on climate change.

But the last two weeks might change all of that.

Hurricane Sandy affected so many people that climate change popped up in many new conversations. Click on these questions to find some of these headlines:

• Was the storm caused by climate change?
• Are humans to blame?
• Will global warming bring more “frankenstorms” like Sandy?
• How can cities protect themselves?
• What are some of the financial impacts?
• How can communities adapt to a new normal of storms like these?
• How do we find stormproof solutions?

Will Obama’s second term allow him to speak more freely (and more urgently) about climate change? Scientific American says that we’ll likely only see “more of the same.” But New Scientist has some suggestions about how he can create a “climate change legacy.” And Brandon Keim, in Wired, sees opportunity for the President:

A cap-and-trade system for carbon pollution is unlikely, but other approaches are possible, from adapting infrastructure and improving post-disaster resilience to revenue-neutral carbon taxes and reduced fossil fuel subsidies.

Let’s hope these conversations start quickly (the Academy’s Peter Roopnarine blogs about climate change, providing many conversation starters). According to recent news headlines (here and here), we’re quickly looking at worst-case scenarios for global warming.

What do you want to say about climate change? Share below.

Image: NOAA

It all has to do with an experiment in the Indian Ocean in 2004. Scientists dumped seven tonnes of iron into an eddy in the Southern Ocean. As expected, an algal bloom followed. Scientific American describes this well:

A hunger for iron rules the microscopic sea life of the Southern Ocean surrounding ice-covered Antarctica. Cut off from most continental dirt and dust, the plankton, diatoms and other life that make up the broad bottom of the food chain there can’t get enough iron to grow.

The bloom was dominated by diatoms like the one pictured above. This group of algae are known to form large, slimy aggregates (marine snot) with high sinking rates at the end of their blooms. Indeed, after about a month, over 50% of the bloom sank deeply into the ocean, taking carbon dioxide with it as it went.

Science News quotes Victor Smetacek, lead author in the study, as saying:

“Every one atom of iron removed 13,000 atoms of carbon” from the air.

While scientists suspected this, they were never able to prove it. This is likely what happened during past ice ages. The air was cooler and drier then and carried more iron-containing dust from the continents to the ocean—lavishly supplying marine phytoplankton and removing carbon, cooling the atmosphere.

Now scientists are wondering if we can cool our warming climate by simply adding iron to the ocean. National Geographic has more on this geoengineering fix and other extreme geoengineering ideas to fight global warming. If only we spent this much energy on stopping global warming…

Image: Marina Montresor, SZN, Alfred Wegener Institute