PORTLAND, Maine — While drought cripples agriculture in the American Midwest, New England has seen an 85 percent increase in extreme downpours over the past six decades — and both troubling weather patterns can be blamed on global warming, a group of scientists, environmental advocates and politicians said Tuesday.

Democratic Rep. Chellie Pingree joined state Sen. Justin Alfond, D-Portland, and John Jemison of the University of Maine Cooperative Extension for the unveiling of Environment Maine’s latest report. The environmental advocacy group released a study following the increases in frequency and intensity of rain and snowstorms from 1948 through 2011.

“Extreme” precipitation events were defined in the study as “those expected to occur no more than once per year on average at a particular location based on the historical record.”

According to the report, severe rain and snowstorms have skyrocketed in frequency in New England over the study period, far outpacing increases in downpours seen in other parts of the country. The mid-Atlantic states saw a 55 percent uptick in the storms over the 64-year stretch and the five regions outlined between Ohio and Nevada saw increases between 26 percent and 36 percent.

The South Atlantic states saw a 17 percent jump in severe rainstorms while the three Pacific Coast states crept up by only 6 percent over that time period.

Ben Seel, Environment Maine clean energy coordinator, told reporters Tuesday that Maine has seen a 74 percent climb in the frequency of extreme rain or snowstorms from 1948 through 2011.

“In other words, severe rainstorms that used to hit Maine once every 12 months now hit Maine once every 6.9 months on average,” he said. “And scientists tell us that that trend toward heavy rainstorms is clearly linked to global warming. We need to heed scientists’ warning that these more frequent heavy rainstorms are linked to global warming and do everything we can to reduce carbon emissions.”

Seel evoked the recent storms and resultant flooding in Brownville, which initial estimates said caused as much as $1.2 million in damage, to illustrate his point. The damage to Brownville and neighboring communities fell short of the required $1.8 million in public infrastructure damage to qualify for federal assistance.

“In the 20th century, flooding caused more property damage and loss of life than any other type of natural disaster,” he said.

Pingree, who owns a farm on North Haven, and Jemison told the assembled media Tuesday the change in weather over New England is problematic for farms and agricultural operations, although in a much different way than the droughts afflicting the midwestern states.

Jemison said warmer winters — the Environment Maine report noted that nine of the 10 warmest years on record have occurred since 2000 — have led to increases in the number and variety of insects farmers must defend against. He said muddier springs make it difficult for farmers to plant or access their crops, while inconsistencies in the summer rains alternate between drowning and drying them out.

“We don’t need rapid rainstorms that come out of nowhere, we need gentle soaking rains that come at routine moments throughout the summer,” Pingree said.

The Environment Maine report attributes the changes in precipitation to global warming, saying that warmer temperatures increase evaporation and allow the air to hold more water. The study states that the water content of the atmosphere is increasing at a rate of about 1.3 percent per decade, sapping the soil of the moisture it needs for crops and building up humidity until extreme storms become unavoidable.

“Given the severe droughts in the Midwest, it’s important to understand that bigger rainstorms or snowstorms do not mean more water will be available for us,” Seel said. “Scientists actually predict that as global warming intensifies, longer periods of relative dryness will be between the extreme rainstorms, increasing the risk of drought. The same increase in evaporation that leads to more water in the air also leads to drier soils.”

Added Pingree: “Scientists tell us — and I’m actually one of those people who believe them — that global warming causes increased evaporations that cause drought conditions in the middle of the country, and all of that evaporation gets dumped into a downpour that just becomes runoff. That’s not a successful way to run an agricultural system, and it’s not a good sign for any of us.”

Also on hand Tuesday was Dr. Johan Erikson, professor of environmental science at Saint Joseph’s College in Standish. Erikson said he did not contribute to the study but was asked to review it for scientific merit. He said Environment Maine’s “research methodology … was excellent.”

Erikson said that while the degree to which humans have contributed to global warming remains ripe for political debate, the data on temperature increases as well as the frequency of rain and snowstorms are “really straightforward science.”

“The public should have no problem accepting the significance of this study,” he said.

Those who spoke at the news conference Tuesday said the report reinforces the need to reduce greenhouse gas emissions in vehicles and power plants, as well as fund research into renewable energy sources.

The report calls for federal and state governments to adopt limits on global warming pollution that would reduce emissions to at least 35 percent below 2005 levels by 2020, and by at least 85 percent by 2050.

Pingree touted recent U.S. Environmental Protection Agency rules capping carbon dioxide emissions at new power plants at 1,000 pounds per megawatt produced — down from an average of 1,800 pounds currently — and reducing the plants’ sulfur dioxide emissions by 74 percent by 2014.

Seth Koenig

Seth has nearly a decade of professional journalism experience and writes about the greater Portland region.