Warming

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Zooming in on L.A.’s Warming Climate

First-of-its-kind study breaks down predictions for 27 L.A. microclimates

Kimberly Ayers

Green roofs like this one at Vista Hermosa City Park are part of the solution for Los Angeles

Listen to the radio version of this story on The California Report.

The City and County of Los Angeles now have customized climate predictions, thanks to a new UCLA study that took global climate science and made it local. A UCLA supercomputer ran for eight months to downscale 22 different global climate models, distilling them into a surgically precise look at L.A. County and beyond. It’s a new kind of Hollywood close-up and it’s a sobering one: temperatures will rise in areas of Los Angeles County by an average of 4 to 5 degrees by mid-century.

Commissioned by the city of Los Angeles, funded by a U.S. Department of Energy grant and conducted by UCLA’s Department of Atmospheric and Oceanic Science, the study focused on forecasting for the metro area between 2041 and 2060. But instead of relying on the global climate model grids that use data from 100 kilometer-square cells of the earth’s surface, the UCLA team’s “quintillion-plus” calculations — yes, that’s with 18 zeros — zoom in to a resolution of 2 square kilometers, just over a square mile.  So instead of data and forecasting for the whole county, you can talk specifically about climate change for Corona, for example. Continue reading

Study: Western Streams Resist Influence of a Warming Climate

Streams show varied response

Josh Simerman, Flickr

Hot Creek, near Mammoth Lakes, was one of 20 streams in the Western U.S. examined in a study by Oregon State researchers who found no clear relationship between increasing air temperatures and stream temperatures.

Rising sea levels, melting glaciers, intensifying storm events – evidence is mounting that the effects of a warming planet will be far-reaching and potentially catastrophic. But one natural system may be more resilient than others when it comes to global warming: mountain streams.

Researchers from Oregon State University report in the journal Geophysical Research Letters that small streams in the western United States have not heated up in response to the region’s warming air temperatures.

Water temperature is a critical variable for aquatic ecosystems. Some fish, for example, time egg-laying to minute changes in water temperatures; in other species, stream temperatures are a key factor in determining the sex of juvenile fish. Continue reading

International Agency Issues Dire Warning

Gretchen Weber

Navajo Generating Station, near Page, AZ

By Susanne Rust

Just as the federal government released its annual index of greenhouse gases, showing a steady increase over the past 21 years, the International Energy Agency warned that we are on the path to 11-degree warming if we don’t curb emissions now.

“Delaying action is a false economy: For every $1 of investment in cleaner technology that is avoided in the power sector before 2020, an additional $4.30 would be needed to be spent after 2020 to compensate for the increased emissions,” the authors of the energy agency report wrote in their 2011 World Energy Outlook.
Continue reading

Global Warming, in Color

Berkeley Earth

Berkeley Earth

The head of the Berkeley Earth Surface Temperature (BEST) study, Richard Muller, a Berkeley physicist previously known for his skeptical views on anthropogenic warming, appeared on Capitol Hill Monday, for the first time since the release of the study’s results.

As we’ve reported, the study found that the Earth is warming. Surface temperatures have increased about one degree Celsius since the mid 1950s, according to the study, which relied on a database of 1.6 billion records. Continue reading

What’s Up With This Weather?

While most of the nation bakes, California keeps its cool–and not just along the coast

Climate scientist Phil Duffy and meteorologist Jan Null joined Michael Krasny on KQED’s Forum to discuss California’s cooler-than-usual summer and what it might reveal about climate change in the region. The upshot? We don’t really know.

“I think we’re seeing plain old climate variability,” said Duffy, who is a visiting scholar at Stanford and the Carnegie Institution for Science and chief scientist for Climate Central, a Climate Watch content partner.

Null agreed with Duffy, saying that in any given year, “stuff happens,” which can’t necessarily be attributed to a larger trend.

“It’s hard to take an individual year and say ‘This is the result of climate change’,” said Null. “It could be just the roll of the dice. If we see a lot of stuff happening over the next decades, then we’re talking about climate change.”

Null said this summer’s cool weather is due to a persistent trough of low pressure along the west coast.

“Anytime you have that for an extended period of time, you get what people call ‘unusual’ or ‘freakish’ weather,” he said. Continue reading

Joshua Trees Losing Ground, Fast

Joshua trees in Eureka Valley, CA (Photo: Ken Cole, USGS)

Joshua trees, the spiky desert-dwellers that are so iconic to Southern California’s dry country that they got a national park named after them, will likely disappear from 90% of their current range by the end of the century, according to a new study by scientists at the US Geological Survey.

Ecologist Ken Cole, the study’s lead author, said that means no more Joshua Trees in Joshua Tree National Park, which is currently in the southernmost part of the species’ range. It also means elimination of the trees across wide swathes of other parts of Southern California as well as Nevada and Arizona.

Cole and his team used climate models, field work, and the fossil record to project the future distribution of Joshua trees. They compared the projected increase in temperatures for the Southwest (four degrees Celsius, according to a “middle of the road” IPCC scenario) to a similar rapid increase in temperatures nearly 12,000 years ago, at the end of the ice age.

Using fossil sloth dung and packrat midden, the scientists reconstructed how Joshua trees responded to that warming. (Sloths, which are now extinct in the region, and packrats, ate the Joshua tree fruit, spreading the seeds and leaving them behind for the scientists to track.) Continue reading

Melting Ice Sheets Spur Sea Level Rise

By Michael D. Lemonick

A new study says melting ice sheets will likely be “the dominant contributor to sea level rise in the 21st century.”

A tidewater glacier in Greenland, pictured in 2008. (Photo: Michael Lemonick)

About 110,000 years ago, global sea level began to drop as the planet cooled, and evaporating seawater was transformed into massive ice sheets that covered large parts of the Northern Hemisphere. About 10,000 years ago, the Earth warmed up again. The ice retreated dramatically, and sea level rose. Since then, the planet’s ice, and the level of the ocean have been more or less stable.
Continue reading

NASA: 2009 Tied for Second-Warmest Year

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Parts of the northern hemisphere may have had an extremely cold December, but nevertheless, last year tied for the second-warmest in 130 years of global instrumental temperature records, according to the latest surface temperature analysis of the NASA Goddard Institute for Space Studies (GISS).  The analysis finds that global temperatures were so similar in 1998, 2002, 2003, 2006, 2007, and 2009, that they are all tied for second place. In the Southern Hemisphere, 2009 set the record as the warmest year, according to this report.

James Hansen, head of NASA’s GISS, and his team have released their end-of-year summary for 2009, initially posted on the Real Climate blog.  It’s pretty dense, but here are some additional highlights:

– The scientists offer an explanation for an apparent data discrepancy over whether 1998 or 2005 was the warmest year.  In short, it comes down to the difference in the way GISS and HadCRUT (Hadley Centre/University of East Anglia Climatic Research Unit) assign or do not assign temperature data for areas without observing stations.  (HadCRUT leaves them out of the analysis, while GISS assigns values based on various factors outlined in the summary.)  GISS maintains that 2005 was the warmest year.

– According to the report:

“There were strong negative temperature anomalies at middle latitudes in the Northern Hemisphere, as great as ‐8°C in Siberia, averaged over the month. But the temperature anomaly in the Arctic was as great as +7°C.”

In other words, 2009’s cold December in certain areas of the planet, as well as an unusually cold 2009 summer in the United States and Canada, do not reflect overall global temperatures nor signal a cooling trend:

“It is obvious that in December 2009 there was an unusual exchange of polar and mid‐latitude air in the Northern Hemisphere. Arctic air rushed into both North America and Eurasia, and, of course, it was replaced in the polar region by air from middle latitudes. The degree to which Arctic air penetrates into middle latitudes is related to the Arctic Oscillation (AO) index, which is defined by surface atmospheric pressure patterns…”

According to GISS data, December 2009 was the most extreme negative Arctic Oscillation since the 1970s.

– The report underscores that monthly temperature anomalies tend to be greater than seasonal anomalies and that the the mean temperature of a particular month might not be the best way to identify global warming. Instead, one needs to look at measurements over the long-term, which, according to GISS data, indicate general warming over at least the last 50 years, just about everywhere on the planet.

The summary concludes with a sort of admonishment:

“The bottom line is this: there is no global cooling trend. For the time being, until humanity brings its greenhouse gas emissions under control, we can expect each decade to be warmer than the preceding one. Weather fluctuations certainly exceed local temperature changes over the past half century. But the perceptive person should be able to see that climate is warming on decadal time scales.”

BK Franchise Serves Up Some “Baloney”

I know: This didn’t happen in California, so why mention it? Well, sometimes stories come in that just seem to crystallize the persistent (some polling would suggest growing) public division over climate change and this is a good example.

When signs on Burger King outlets started opining that “Global warming is baloney,” a Memphis reporter decided to check it out. His exchanges with the local burgermeister and the parent company make for pretty amusing reading.

Interesting that while polls taken within the last year have indicated flagging faith in the prevailing view of climate scientists that the world is warming, a spring poll by the Pew Research Center showed 59% of Americans supporting some kind of cap on carbon emissions. Though still sharply divided along party lines, that could indicate that some kind of reluctant consensus is forming around the issue.

Short-Term Data Clouds the Climate Picture

Two established climate scientists have issued a warning about using short-term data in arguments over climate change. This is such a common point of confusion that I’ve published the news release from Lawrence Berkeley National Lab, in its entirety:

BERKELEY, CA – In the hotly debated arena of global climate change, using short-term trends that show little temperature change or even slight cooling to refute global warming is misleading, write two climate experts in a paper recently published by the American Geophysical Union–especially as the long-term pattern clearly shows human activities are causing the earth’s climate to heat up.

In their paper “Is the climate warming or cooling?” David R. Easterling of the National Oceanographic and Atmospheric Administration’s National Climatic Data Center and Michael Wehner of the Computational Research Division at the Department of Energy’s (DOE) Lawrence Berkeley National Laboratory note that a number of publications, websites and blogs often cite decade-long climate trends, such as that from 1998-2008, in which the earth’s average temperature actually dropped slightly, as evidence that the global climate is actually cooling.

However, Easterling and Wehner write, the reality of the climate system is that, due to natural climate variability, it is entirely possible, even likely, to have a period as long as a decade or two of “cooling” superimposed on the longer-term warming trend. The problem with citing such short-term cooling trends is that it can mislead decision-makers into thinking that climate change does not warrant immediate action. The
article was published April 25 in Geophysical Research Letters.

“We wrote this paper, which was carefully reviewed by other researchers and is scientifically defensible, to clearly show that even though our climate is getting warmer, we can’t expect it to do so in a monotonic way–or that each year will be warmer than the preceding year,” said Wehner. “Even with the climate changes caused by human activity, we will continue to see natural variability including periods of cooler temperatures despite the fact that globally averaged temperatures show
long-term global warming.”

“It is easy to ‘cherry pick’ a period to reinforce a point of view, but this notion begs the question, what would happen to the current concerns about climate change if we do have a sustained period where the climate appears to be cooling even when, in the end, the longer term trend is warming?” write Easterling and Wehner.

The research was funded by the DOE Office of Science’s Office of Biological and Environmental Research through its Climate Change Prediction Program.

Citing an accepted climate modeling scenario in which no efforts are made to reduce the amount of greenhouse gases released into the atmosphere, the earth’s climate is expected to warm by 4 degrees Celsius (7.2 degrees Fahrenheit) by the end of the 21st century. The authors point out that this is consistent with other simulations contained in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC 2007), which was recognized with the 2007 Nobel Peace Prize.

“Climate scientists pay little attention to these short-term fluctuations as the short term ‘cooling trends’…are statistically insignificant and fitting trends to such short periods is not very meaningful in the context of long-term climate change,” the authors write. “On the other hand, segments of the general public do pay attention to these fluctuations and some critics cite the most recent period as evidence against anthropogenic-forced (human-induced) climate change.”

The authors used both observed climate data from 1901-2008 and a series of climate model simulations performed on supercomputers to study the occurrence of decade-long trends in globally averaged surface air temperature. They found that it is possible, and indeed likely, to see periods as long as a decade in the recent past which do not show a warming trend. The authors even found that running computer simulations for the 21st century with significant increases in greenhouse gas emissions showed some decades with lower or static average temperatures. One such example can be found by looking at data from 1998 to 2008, which shows no real trend, even though global temperatures remain well above the long-term average.

According to the authors, the unusually strong 1997-98 El Niño contributed to unusual warmth in the global temperature for 1998, so that without similar dramatic changes, the following decade does not appear to be warming. A similar interpretation can be made by looking at the short-term data from 1977-85 or 1981-89, “even though these periods are embedded in the 1975-2008 period showing a substantial overall
warming,” Easterling and Wehner write. In the first example, dropping data from 1998 and looking at 1999-2008, the researchers found a strong warming trend.

Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.

Editors’ Note: Of course, this cuts both ways. Though it may be tempting to do so, it’s no more legitimate to point to the latest heat wave or a single fire season as proof of global warming. This is a conundrum that makes it difficult to find consensus on pubic policy. There are additional links posted with the full news release at the LBNL site.