Hurricane Isaac reaches shore

A powerful storm bearing down on the Gulf Coast and New Orleans is now a hurricane, US forecasters say.

Hurricane Isaac boasts sustained winds at least 75mph (120km/h), and is likely to make landfall by Tuesday night.

The storm is expected to hit New Orleans seven years after the much stronger Hurricane Katrina.

US President Barack Obama has warned residents in the path of the storm they should not "tempt fate" and should heed evacuation warnings.

At 11:20 CDT (16:20 GMT), the storm was 160 miles (250km) south-east of New Orleans, moving north-west at 10mph (17km/h).

Mr Obama has declared an emergency in Louisiana, allowing federal funds to be released to local authorities.

"As we prepare for Isaac to hit, I want to encourage all residents of the Gulf Coast to listen to your local officials and follow their directions - including if they tell you to evacuate," Mr Obama said on Tuesday.

Speaking from the White House, he added: "Now is not the time to tempt fate. Now is not the time to dismiss official warnings. You need to take this seriously."
 
Storm surge
Shortly after Isaac reached hurricane status, Louisiana Governor Bobby Jindal called for the Federal Emergency Management Agency (Fema) to make a full emergency declaration for the state.

He told reporters that a declaration made on Monday did not allow for the reimbursement for state's expenses from the storm.

"We have learned from past experiences that you cannot wait and you have to push the federal bureaucracy," Mr Jindal, who cancelled an appearance at the Republican National Convention because of the storm, said.

Isaac has killed at least 24 people in Haiti and the Dominican Republic, and caused significant flooding and damage in the Caribbean.

It largely bypassed the Republican convention in Tampa, Florida, but prompted a day-long delay to proceedings there.

The National Hurricane Center warned that a possible combined "storm surge" and high tide would cause flooding in coastal areas along the Gulf Coast.

Water would potentially reach 6-12ft (1.8-3.7m) above ground in south-west Louisiana and Mississippi, 4-8ft in Alabama and 3-6ft in south-central Louisiana.

Isaac is also threatening heavy rainfall of as much as 20in (51cm) in isolated spots, and could spark possible tornadoes along the northern Gulf Coast.

Hurricane warnings are in place for a swathe of land 400 miles (645km) wide, from Morgan City in Louisiana to the Florida-Alabama state line.

2012 US Meteorological Society: Information Statement on Climate Change

CNN Video footage of Hurricane Isaac

There is unequivocal evidence that Earth’s lower atmosphere, ocean, and land surface are warming; sea level is rising; and snow cover, mountain glaciers, and Arctic sea ice are shrinking.

The dominant cause of the warming since the 1950s is human activities. This scientific finding is based on a large and persuasive body of research.

The observed warming will be irreversible for many years into the future, and even larger temperature increases will occur as greenhouse gases continue to accumulate in the atmosphere.

Avoiding this future warming will require a large and rapid reduction in global greenhouse gas emissions.

The ongoing warming will increase risks and stresses to human societies, economies, ecosystems, and wildlife through the 21st century and beyond, making it imperative that society respond to a changing climate.

To inform decisions on adaptation and mitigation, it is critical that we improve our understanding of the global climate system and our ability to project future climate through continued and improved monitoring and research.

This is especially true for smaller (seasonal and regional) scales and weather and climate extremes, and for important hydroclimatic variables such as precipitation and water availability.

Technological, economic, and policy choices in the near future will determine the extent of future impacts of climate change.

Science-based decisions are seldom made in a context of absolute certainty. National and international policy discussions should include consideration of the best ways to both adapt to and mitigate climate change.

Mitigation will reduce the amount of future climate change and the risk of impacts that are potentially large and dangerous. At the same time, some continued climate change is inevitable, and policy responses should include adaptation to climate change.

Prudence dictates extreme care in accounting for our relationship with the only planet known to be capable of sustaining human life.

[This statement is considered in force until August 2017 unless superseded by a new statement issued by the AMS Council before this date.]

Read the report in PDF format:  pdf version

Read the full online report here: 2012 AMS Information Statement on Climate Change