By the time climate change reduces crop yields or frequently floods New York City subways, it would be too late to avert damage without better forecasting tools, a panel of scientists said in a report released today.

Dangerous rises in the sea level or heat waves that kill crops can arrive quickly and leave little time to put preventative measures in place, according to a study from the National Research Council, a group of scientists providing information for U.S. government decision-makers.

The report – one of two issued today on climate change – calls for an early warning system to monitor climate conditions and improved models for predicting changes that impact the way people live. The alerts could be modeled on such programs as the National Integrated Drought Information System created by Congress in 2006 or the U.S. Agency for International Development’s Famine Early Warning System Network.

“It’s important to look down the road and try to identify what are the abrupt changes that we can plan for with some degree of confidence, and then make the best of them rather than having them hit us in the face,” said Anthony Barnosky, professor of integrated biology at the University of California in Berkley and a co-author of the report.

Hansen Report

In a separate report today, James Hansen, who warned of the dangers of global warming as early as 1988, said a United Nations-endorsed target of capping global warming is too high and will ensure future generations suffer “irreparable harm.”

Even limiting warming to 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial times would submerge coastlines, cause the mass extinction of species and trigger extreme weather, according to Hansen, former director of the NASA Goddard Institute for Space Studies and co-author of the report published today in the journal PLOS One.

Quick action, including a fee on carbon dioxide emissions and the expansion of nuclear power, is needed to prevent the worst impacts of climate change, according to the paper.

“Two degrees Celsius warming above pre-industrial, which would mean about 1 degree Celsius warming above the present, creates a significantly different planet with enormous consequences, including eventually the un-inhabitability of coastal cities,” Hansen, adjunct professor at New York’s Columbia University’s Earth Institute, said at a briefing. “There’s no recognition of this in government policies.”

Ocean Monitoring

The planet’s rapid warming is already producing adverse results. The loss of Arctic sea ice is under way as atmospheric levels of carbon dioxide continue to rise, according to Barnosky. Other impacts, such as sea-level rise from ocean warming, will probably to take longer and may be predicted with better satellite data and ocean monitoring.

“There’s nothing in place to put all the pieces together in a way that really integrates the information to make it meaningful for this sort of longer-term prediction,” Barnosky said.

Barnosky recommends that the U.S. government create an Abrupt Change Early Warning System using many existing resources.

Record carbon emissions have lifted the Earth’s temperature about 0.8 degrees Celsius (1.4 degrees Fahrenheit) since the industrial revolution, and the planet is on a path to exceed the UN-endorsed maximum of 2 degrees Celsius of warming by 2100. Scientists say as a result, sea levels are rising and oceans are acidifying.

Faster Extinctions

Scientists predict that the planet will experience more extreme weather, including frequent droughts and stronger storms.

Absent action by governments around the world “the future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered,” according to the report.

Those changes mean there is a high probability for a faster pace of extinctions of sea and land species in this century.

“We tend to think of climate change as being this gradual linear process,” Barnosky said. “What you have to think about are threshold effects, tipping points. If you can see that coming you can begin to think about how to adapt.”

Fossil Data

Changes can occur over periods as short as decades, or even years, a fact confirmed by research into Earth’s history, according to the report. Data from fossils, sediment cores, and ice cores reveal the abrupt end of a millennium-long cold period about 12,000 years ago associated with the extinction of 72 percent of the large-bodied mammals in North America.

The National Research Council acknowledges that there remains uncertainty over how quickly the impacts of climate changes will unfold. For example, warming from the release of methane trapped in frozen soil and ice, once thought likely to occur in this century, is now regarded as a lesser contributor to climate change, according to the report.

“We need to prepare for the reals risks that we are heading into a dangerously warming world,” Peter Frumhoff, chief scientist at the Cambridge, Massachusetts-based Union of Concerned Scientists, said in an interview. “Whether it’s even more urgent than we thought, which is the point of Jim’s paper, or as urgent as we’ve all realized, the mitigation prescription is the same – swift deep emissions reductions as quickly as possible.”

Diplomats from almost 190 nations last month endorsed a set of measures on global warming, laying the groundwork for a treaty to be adopted in 2015 that would limit pollution by all nations for the first time.

The delegates at a United Nations conference sidestepped the most controversial issues in the debate, namely how to divide up responsibility for emissions cuts and how richer nations will meet their promise to channel $100 billion a year by 2020 in aid for climate projects.