WASHINGTON » The Asia-Pacific region can expect increased droughts and floods in the next 20 years — often in the same spots — as well as rising sea levels and more intense tropical storms, Honolulu academics told a gathering of scientists here Friday.

And while governments increasingly view global climate change as a national security threat, a communications chasm still divides researchers and security specialists, the panelists warned.

"Other possible impacts of climate change include increases in human diseases as tropical diseases move northward and the possibility of climate-induced migration, primarily due to changes in water and food supplies," said J. Scott Hauger, an associate professor with the Asia-Pacific Center for Security Studies in Honolulu.

Hauger and Virginia Watson, also with the center, took part in a 90-minute presentation at the annual meeting of the American Association for the Advancement of Science. Their topic was "Science and Policy for Environmental Security in the Asia-Pacific Region."

At the heart of the issue is the steady increase in atmospheric carbon dioxide, measured since the late 1950s at Mauna Loa Observatory on the Big Island. Scientists have warned of a correlating rise in average atmospheric temperatures, the greenhouse effect.

That link, as well as forecasts of dire results such as rising sea levels, still has skeptics. But Hauger noted that the Pentagon’s Quadrennial Defense Review recognized climate change as a security threat for the first time in 2010.

Panelist Hiroshi Nagano, of Japan’s National Graduate Institute for Policy Studies, said his government has acknowledged since 1980 that "threats are not only military in nature" and can include natural disasters and food and energy shortages. More recently recognized as a possible threat, he said, is the spread to humans of avian flu by mosquitoes feeding on snipes and plovers migrating from Siberia.

While the long-term effects of global climate change still are open to debate, the near-term effects are not, said Hauger.

"Over the next 20 years, we know pretty much what’s going to happen," he said. "The best-case scenarios and the worst-case scenarios differ very little in terms of the average global warming. But if you get out toward the end of the century, then the best-case scenarios and the worst-case scenarios can differ very drastically, and that depends primarily on the additional amount of greenhouse gases that we pump into the atmosphere in the interim."

Rising ocean temperatures will lead to more heat feeding tropical cyclones and greater evaporation and rainfall rates — which will lead to flooding, and rising sea levels from the thermal expansion of ocean water, he said.

Higher air and sea temperatures will lead to the melting of ice caps and glaciers, and snow will melt faster in the spring, he said. Some areas will get less rain, others more.

"Interestingly enough, many of the same areas that are subject to drought are those areas that are also subject to flood," said Hauger. "So double whammies are possible."

The islands of Kiribati in the Pacific and the Maldives in the Indian Ocean are already facing higher sea levels, he noted.

One particularly vulnerable area is the Mekong Delta, Vietnam’s rice basket, home to 20 million people, said panelist Peter Backlund, director of the Integrated Science Program at the National Center for Atmospheric Research in Boulder, Colo.

Rising seas or floods there could lead to massive migration and hunger. Yet the population of coastal areas, especially coastal cities, is growing in the region.

"More people are moving into harm’s way," said Backlund. "The problem is getting worse."

Water is as big a concern as food, the panelists agreed.

"You’ll find that countries are pursuing very different trajectories," said Watson. "But you see that the complex environment of security cannot be understood without high policy consideration of water solutions."

Especially worrisome is a possible tipping point, where the effects of global warming begin to accelerate, Hauger said. That could come with the release of methane, another greenhouse gas, from thawed permafrost and from the loss of polar ice, which reflects sunlight back into space.

A change in salinity in the North Atlantic could shift the flow of the Gulf Stream, which would give Western Europe the same climate as Siberia, Hauger said.

"This set of climate effects, including retreating glaciers, thinning ice caps, rising sea levels, heavy precipitation events, more intense and longer droughts, can have human impacts in the form of degradation of fresh water resources, a decline in food production, increase in storm and flood disasters and environmentally induced migration," said Hauger. "And these of course are events that, as they occur, the policy community, the security community is going to have to deal with."

The Asia-Pacific Center for Security Studies, based at Fort DeRussy, is a Defense Department academic institute that invites military and civilian representatives from the region in for classes and conferences that look for peaceful solutions to security issues.