Warmer Temperatures Threatening CA Fruit Crops?
Almond trees in winter, Photo by Sasha Khokha
Increasingly warmer temperatures in the Central Valley could pose a serious threat to California's fruit and nut crops in the not-too-distant future, according to a new study out of UC Davis. The study finds that winter chill, which is an important factor in the productivity of tree crops, is likely to decrease by more than 50% by 2100, making the region less hospitable for crops like walnuts, peaches, plums, and cherries, unless changes in growing techniques are adopted.
Tree crops go dormant in the winter when temperatures drop to a certain level for a certain period of time. Each crop then needs a certain number of 'chilling hours' - between 32 and 45 degrees Fahrenheit - in order to break dormancy and resume growth.
If crops don't recieve their specific chilling requirement during the winter, problems arise. Flowering time is disturbed, which could be devastating for crops such as walnuts and pistachios that depend on simultaneous male and female flowering for pollination. And if crops don't recieve enough winter chill to go dormant in the first place, they will continue producing buds and sprouting branches, but they may not yield fruit, having dire consquences for California's $7.8 billion fruit and nut industry, explained study author Minghua Zhang.
"We hope that people will take this study as a wake up call," said Zhang. "Crops are going to be seriously impacted."
Zhang and her fellow reaserchers found that in certain parts of the Central Valley, winter chill declined by nearly 30% between 1950 and 2000. They expect that the decline will be 60% by 2050 and 80% by the end of the century.
"There is a problem coming up that we need to prepare for," said Eike Luedeling, another of the study's authors. "So far low chilling requirement haven't even been a breeding goal, but we are going to need a long-term strategy to cope with this."
The researchers found that by 2000, winter chill had declined to the point that only 4% of the Central Valley was suitable for growing apples, cherries, and pears, down from 50% earlier in the 20th century. They predict that by the end of the century, the region might no longer be suitable for growing these crops as well as walnuts, pistachios, peaches, plums, and apricots. Crops like almonds and pomegranates will most likely be affected the least, as they have low winter chill requirements.
NOAA Confirms El Nino
Warm water patterns in the Pacific during normal (upper) and El Nino (lower) years. The lower image is from 1995-96. Image from NASA
Scientists with the National Oceanic and Atmospheric Administration today confirmed what many had pretty much surmised: El Nino is back.
Officially the El Nino Southern Oscillation (ENSO), the cyclical pattern of ocean conditions has broad implications for weather and the Pacific food chain.
According to the NOAA news release:
"NOAA expects this El Niño to continue developing during the next several months, with further strengthening possible. The event is expected to last through winter 2009-10."
NOAA's Climate Prediction Center suggested about a month ago that conditions were right for the return of El Nino.
More recently, the high incidence of underweight sea lion pups turning up along the California coast was taken by some as a harbinger of ENSO. During El Nino cycles, normal upwelling of deep, cold water slows down, essentially shutting down the "food elevator" for many species.
Of course, there can be an upside. According to NOAA:
"El Niño's impacts depend on a variety of factors, such as intensity and extent of ocean warming, and the time of year. Contrary to popular belief, not all effects are negative. On the positive side, El Niño can help to suppress Atlantic hurricane activity. In the United States, it typically brings beneficial winter precipitation to the arid Southwest, less wintry weather across the North, and a reduced risk of Florida wildfires."
Links to climate change are less clear. Some scientists have suggested that warming air and sea temperatures might bring about more and longer El Nino events.
Parsing the White House Climate Report
At least one researcher cited in the 196-page climate impacts report issued this week by the Obama administration is not impressed with the final product. Roger Pielke of the University of Colorado's Center for Science & Technology Research has written a blog post critical of the report and in particular, the way in which his work was interpreted. If you'd rather not plow through the entire post, John Tierney has an overview of Pielke's critique on his blog for the New York Times.
2004 California heat wave, from the Aqua satellite. Image: NASA
The report was arguably the first to break down both observed and projected effects of climate change into coherent regional summaries. For the purposes of the report, California was considered part of the Southwest region, which included states as far east as Colorado and New Mexico.
Not surprisingly, many of the points raised in the Southwest section (beginning on p. 129) have to do with water supply. Most have been reported or discussed in our Climate Watch coverage, either here or in our radio reports. Selected "highlights" include:
- Past climate records based on changes in Colorado River flows indicate that drought is a frequent feature of the Southwest, with some of the longest documented “megadroughts” on Earth.
- The prospect of future droughts becoming more severe as a result of global warming is a significant concern, especially because the Southwest continues to lead the nation in population growth.
- Human-induced climate change appears to be well underway in the Southwest. Recent warming is among the most rapid in the nation, significantly more than the global average in some areas.
- Projections suggest continued strong warming, with much larger increases under higher emissions scenarios compared to lower emissions scenarios. Projected summertime temperature increases are greater than the annual average increases in some parts of the region, and are likely to be exacerbated locally by expanding urban
heat island effects.- Water supplies in some areas of the Southwest are already becoming limited, and this trend toward scarcity is likely to be a harbinger of future water shortages. Groundwater pumping is lowering water tables, while rising temperatures reduce river flows in vital rivers including the Colorado.
- Projected temperature increases, combined with river-flow reductions, will increase the risk of water conflicts between sectors, states, and even nations.
- Increasing temperature, drought, wildfire, and invasive species will accelerate transformation of the landscape.
- Under higher emissions scenarios, high-elevation forests in California, for example, are projected to decline by 60 to 90 percent before the end of the century.
- In California, two-thirds of the more than 5,500 native plant species are projected to experience range reductions up to 80 percent before the end of this century under projected warming.
- Projected changes in the timing and amount of river flow, particularly in winter and spring, is estimated to more than double the risk of Delta flooding events by mid-century, and result in an eight-fold increase before the end of the century.
- A steady reduction in winter chilling could have serious economic impacts on fruit and nut production in the region. California’s losses due to future climate change are estimated between zero and 40 percent for wine and table grapes, almonds, oranges, walnuts, and avocados, varying significantly by location.
By the way, Pielke's critique does not directly address anything in this list, though his work does involve weather-related disasters, which would include floods. Asked by a commentator on his blog if he thinks the entire report should be dismissed based on the flawed interpretation of his research, Pielke replied: "I wouldn't think so and would certainly hope not. At the same time the section which covers my research does not give me a lot of confidence in the process that led to the report."
The Return of El Nino?
The federal Climate Prediction Center, operated by NOAA, reported this week that current conditions in the Pacific would seem to foreshadow a return to El Nino conditions, possibly within the next few weeks.
2006 El Nino conditions, as observed by the Jason satellite. Photo: NASA
The ocean conditions formally known as ENSO, or the El Nino/Southern Oscillation, arise when normal upwelling of deep, cold water abates, causing warmer surface temperatures (SST).
El Nino and its opposite, La Nina, have far-reaching implications on weather patterns. Here on the West Coast, it usually means wetter winters in southern California and drier ones in the Pacific Northwest. Because northern and central California lie in between, things there can go either way.
El Nino can also have a significant impact on fisheries, as much of the food chain is interrupted when upwelling slows.
Here's a good overview of El Nino "mechanics" from UC Berkeley.
Pika One Step Closer to ESA Listing
American pika. Photo by Chris Ray.
UPDATE: Federal fish & wildlife authorities have decided to proceed with a full review of the American pika, for potential listing under the Endangered Species Act. The US Fish & Wildlife Service will formally publish its decision this week, including this summary:
"We, the U.S. Fish and Wildlife Service, announce a 90-day finding on a petition to list the American pika (Ochotona princeps) as threatened or endangered under the Endangered Species Act of 1973, as amended. We find that the petition presents substantial scientific or commercial information indicating that listing of the American pika may be warranted. Therefore, with the publication of this notice, we are initiating a status review of the species, and we will issue a 12-month finding to determine if the petitioned action is warranted. To ensure that the status review is comprehensive, we are soliciting scientific and commercial data regarding this species. We will make a determination on critical habitat for this species if, and when, we initiate a listing action."
The Center for Biological Diversity (CBD) first petitioned for listing in 2007, and then followed with a lawsuit a year later, when federal authorities shelved the request.
The significance of this week's decision, according to a CBD news release, is that "the pika will become the first mammal considered for protection under the Act due to global warming in the continental United States outside of Alaska."
Last month a San Francisco court ruled that state wildlife officials wrongly denied the CBD's petition for listing under California's ESA. So it looks like the little critter will get a fresh review at both the state and federal levels.
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.
Early Runoff More than Theory
This post has been modified based on clarifications by the study's lead author, which are outlined in her comment, below.
A recent study seems to confirm what many have already surmised: The spring melt from the Sierra snowpack is happening sooner.
To get a handle on the timing of mountain runoff, a team led by Iris Stewart of Santa Clara University pulled together data from 52 stream gauges up and down California. For her study, Stewart says she chose only water courses unaffected by dams and diversions, with at least 20 years of continuous data.
Stewart's data shows that over the 60 years spanning 1948-2008; 80% of the gauges show the "stream pulse" that accompanies peak runoff, coming consistently sooner in the season–an average of about 10 days sooner, though at least one location had shifted up by more than a month. In fact, combining all of the metrics in the study, Stewart says only one gauge showed a later trend.
The trend seems remarkably consistent. Stewart says that despite a warming trend over the past ten years, she has not seen any acceleration of the trend within that period.
Stewart cautions that there's more work to do on this and was reluctant to draw broad inferences from the study. Runoff in a particular stream is affected by many factors, including the elevation, slope, aspect (which direction it's facing), vegetation cover and soil composition. Stewart says further study of these variables will better help identify the most vulnerable streams. But the latest results seem consistent with an earlier study in which Stewart found "earlier runoff on a continental scale."
Scientists are concerned that as average temperatures rise, California's mountains will see more rain, less snow–and what snow there is will melt off sooner. Reservoirs can only retain so much runoff at once, so if more of the "frozen reservoir" dissipates earlier in the season, farms and cities stand to be caught short of water before the rains return.
Stewart, an assistant professor at SCU's Environmental Studies Institute, presented her findings this morning to researchers at the Pacific Climate Workshop (known as PACLIM, the conference does not have a website), a semi-annual gathering of climate scientists doing front-line research around North America. The conference in Pacific Grove is organized by the USGS office in Menlo Park.
Over the course of four days, about 60 researchers will hear findings on the climatic implications for fire, fog, glaciers, the ocean and wildlife, among other topics.
Climate Debate Runs Hot and Cold
We see occasional references in our discussions here to a "cooling phase" over the past decade or so. It's often evoked in arguments against the case for global warming. Of course, in the centuries-long span of the Earth's climate patterns, a decade or so is a mere blip on the screen.
Now a climatologist at Lawrence Berkeley National Lab has co-authored a paper that warns against using "periods of a decade or two" to argue the case one way or the other (we also often hear people use temperature data from recent hotter years as evidence for global warming).
Andrew Revkin summarizes the findings in his blog for the New York Times.
Wehner works in the Computational Research Division at LBNL and co-authored the paper with NOAA scientist David Easterling of the National Climatic Data Center, in Ashville, NC. Easterling wrote the Center's FAQ page on global warming, in which he includes this answer to the question of whether the global climate is warming:
"Global surface temperatures have increased about 0.74°C (plus or minus 0.18°C) since the late-19th century, and the linear trend for the past 50 years of 0.13°C (plus or minus 0.03°C) per decade is nearly twice that for the past 100 years. The warming has not been globally uniform. Some areas (including parts of the southeastern U.S. and parts of the North Atlantic) have, in fact, cooled slightly over the last century. The recent warmth has been greatest over North America and Eurasia between 40 and 70°N. Lastly, seven of the eight warmest years on record have occurred since 2001 and the 10 warmest years have all occurred since 1995."
As for the geographic fluctuations, Robert Bornstein of San Jose State has produced data showing a general cooling trend along the California coast over the past 30 or 40 years. But he's quick to point out that the anomaly is most likely a result of, not an argument against the broader global warming trend.
Ag Rules: Heading Off the Heat
Water cooler imprinted with heat safety tips. Photo: Sasha Khokha
It was like a pageant of farmers in plaid shirts; nearly a dozen speakers in a Fresno County meeting hall, surrounded by vineyards. Farm leaders offered glowing praise of Cal OSHA’s new guidelines and training seminars that will help them comply with the state’s first-in-the nation heat safety rules–passed three years ago.
The love-fest with Cal-OSHA sets a new tone for agriculture. Growers have traditionally been at odds with the agency tasked with protecting the state’s workers. Farmers have challenged fines and complained about inspections. But despite the regulations, six workers died last summer, including a pregnant teenage farmworker (some of the victims worked in construction or other outdoor jobs).
Part of the problem was that neither Cal-OSHA inspectors nor farmers had a very clear understanding of how to implement the rules. Is it enough to have an umbrella folded up in the back of a pickup in case it got hot? How hot? How much shade and water is enough?
Today, Cal-OSHA chief Len Welsh made it clear: when it’s 85 degrees or hotter, shade tents or umbrellas have to go up. And that shade should be no more than a two-and-a-half-minute walk away, according to the rules, which also require enough shade so that one-in-four employees are protected from the sun at any given time.
That’s still worrisome for leaders of the United Farmworkers Union, who were conspicuously absent from the press conference. There are times, they say, when the temperature soars well above 100 or spikes suddenly and everybody should get a break. The UFW says the new guidelines are too vague, and Cal-OSHA’s publicity campaign to educate farmers isn’t enough. Union leaders say the state should impose more fines and criminal penalties when workers die in the heat.
Was 2008 Relatively Warm or Cool?
Answer: Both. It depends on your historical time frame.
With a global average surface temperature of 79 degrees Fahrenheit, 2008 was the coolest year since 2000, according to climatologists at the NASA Goddard Institute for Space Studies (GISS). But it's also the ninth-warmest year since 1880, so it's probably not time to invest in a ski resort just yet.
Including the 2008 dip, the 10 warmest years on record (since 1880) have all occurred between 1997 and 2008, according to NASA.
The NASA scientists attribute 2008's relatively lower temperature to a cooler Pacific Ocean, due to a strong La Nina pattern in the first half of 2008. La Nina and El Nino are opposite phases of a natural oscillation of upwelling and subsequent temperatures in the equatorial Pacific Ocean.
2008 temperatures in the United States were cooler than any other year this decade, but, as illustrated on the map below, other parts of the world such as Eurasia and the Arctic were exceptionally warm.
Director of GISS James Hansen predicts that because a shift to El Nino is expected to start this year or next, it "still seems likely" that we'll see a new record high for the average global surface air temperature in that time frame.
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