Weather forecast for 2011: Unpredictable

Scientists decline to definitively attribute ongoing drought and severe storms to climate change.

stormy night sky 521 (photo credit: Courtesy)
stormy night sky 521
(photo credit: Courtesy)
Another year of drought, severe storms with 100 kilometer-anhour winds and pouring rain, massive forest fires, unending summers of over 40º temperatures that seemingly continue right through fall. All those are familiar weather events from the past year.
The Israel Meteorological Service (IMS) can and will tally the data and provide summaries of the year that has been. There’s an overarching question that should be posed, however. How much of the weather is being influenced by climate change?
Here’s the paradoxical answer according to climate scientists: Even if a severe storm were caused by climate change, it would be unlikely in the extreme that scientists would be able to confirm it, says Prof. Pinhas Alpert, head of the Porter School of Environmental Studies at Tel Aviv University and the coordinator of the GLOWA Jordan River Project, the longest-running climate change study in Israel.
“It would be rare to connect specific weather incidents to climate change,” he says. “Climate is measured in 30-year segments. To say that a specific storm was caused by climate change, you would have to say that in the last 30 years you had never seen a storm like that. Regarding the storm of two weeks ago, we’ve seen other storms like that, even if maybe not for many years.”
To determine if the recent storm was really a product of climate change, 110 years of climate records would have to be combed to determine if the storm was one of a kind.
Even then, “it wouldn’t be responsible to say something about a specific incident,” says Alpert.
So what, then, can be attributed to climate change? Well, temperature changes can be more readily attributed. Again, however, scientists say climate studies do not focus on a specific year. Whether 2010 was the hottest year on record is a matter for the statisticians. What is a matter for climate scientists is the fact that temperatures in the summer have generally been rising for the last 50 years, says Alpert. That does not mean that each year was hotter than the last, but the general trend indicates rising temperatures.
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THE GLOWA Jordan River Project began in 2000 as the only climate change study in the country. It will reach its conclusion next year. Part of the project has been to try to bring regional and local resolution to global climate change models. According to a brief the project produced in 2009, there are two trends that have been observed which scientists expect to continue over the next 50 years.
According to GLOWA’s models, temperatures have risen on average one degree in the last 50 years. In the next five decades, the models predict another one- to two-degree average rise. The models have also predicted a 30 percent drop in average precipitation over the next 50 years and a more significant drop until 2100.
At the same time, those models are not designed to focus on a span of a decade or less.
According to Dr. Amos Porat, of the climate division of the IMS, one of the tasks of his department is to summarize every month and year so that scientists will have the data available to make assessments based on 100 years of data.
“In terms of climate change, a single year is just a dot. To discuss climate change, you need 100 years,” he says. The data over the last 60 to 70 years could indicate an increasing trend, but it could also indicate cycles, Porat points out.
“In the 1960s and ’70s, temperatures were lower. In the 1940s and ’50s, temperatures were higher. Now temperatures are higher again. So is this a trend of increasing temperatures or a cycle?” According to Porat, there is no clear-cut trend of less rainfall, either. While the past seven years have been below average, he says, a similar spate of years occurred in the 1920s and ’30s and again at the end of the 1950s and the beginning of the 1960s.
Moreover, “even if we finish eight or nine years with no rain, we still won’t be able to say whether it’s a trend or not. It’s very important to steer clear of firm conclusions,” he says.
For Porat, what is most important is continuing to collect the data. Without the data, no models and no experiments can be conducted.
THAT IS certainly true for Prof. Hendrick Bruins of Ben-Gurion University of the Negev, who used data from 39 IMS weather stations to measure temperature and rainfall patterns from 1970 to 2002. In a study published in the Journal of Climatic Change in 2009, Bruins found that rainfall along the coast had mainly stayed the same, but inland and in the South it had dropped off somewhat.
“That would be consistent with what we saw during the storm two weeks ago, where the North and the Coastal Plain got a lot of rain but Jerusalem and the Negev were dry,” says Bruins.
He says that according to observations, the climate had gotten warmer as well during that period.
“That’s worrying because it means the country is getting hotter and drier. The risk of drought has increased, and the frequency and intensity of such droughts are also bound to increase. Drought can cause big problems if it becomes protracted and severe,” he says.
While the country has been suffering from less than average rainfall since 2004, Bruins sees a lack of proactive planning as largely to blame, rather than climate change.
“The government should have begun desalinating water much earlier and then refilling the groundwater aquifers to build up reserves.
Instead, the reserves were all used up. The government essentially sold too much water to its citizens and to agriculture,” he asserts.
One of Bruins’s areas of research is disaster studies and contingency planning at the Department of Man in the Desert at the Swiss Institute for Dryland Environmental Research of BGU’s Jacob Blaustein Institutes for Desert Research.
Bruins also derides a simplistic understanding of climate change as totally contingent on the amount of carbon dioxide in the atmosphere.
“Climate is much more complex than just CO2 in the atmosphere. That approach is simplistic and very often erroneous. Climate is a global system of currents in the air and the oceans, as well as many other factors,” he explains.
Bruins points to one phenomenon that occurs in the North Atlantic that affects weather here.
“Northwest Europe is pampered by a warm Gulf Stream from the Gulf of Mexico. The weather in England should be equivalent to that of Canada and the northern US states, but for the most part it hasn’t been. However, now it seems as though the warm Gulf Stream is diminishing in intensity,” he says.
“That’s worrying in Israel because climatic studies that go back thousands of years using indicators show that when the water in the North Atlantic gets cooler, we get drier weather.”
So if you’re looking for the weather forecast for the next day or week, talk to the meteorologists. But what the climatologists can tell you is that over the next 50 to 100 years, it’s a better bet to buy sunscreen than an umbrella.