updated 7/28/2010 4:34:09 PM ET 2010-07-28T20:34:09

Not only was the past decade the warmest on record, but climate indicators being tracked globally are worsening, scientists reported Wednesday in their annual "State of the Climate."

"A comprehensive review of key climate indicators confirms the world is warming and the past decade was the warmest" since recordkeeping began in 1870, declares the report, which was released by the National Oceanic and Atmospheric Administration.

Compiled by more than 300 scientists from 48 countries, the report said its analysis of 10  indicators that are "clearly and directly related to surface temperatures, all tell the same story: Global warming is undeniable."

Concern about rising temperatures has been growing in recent years as atmospheric scientists report rising temperatures associated with greenhouse gases released into the air by industrial and other human processes. At the same time, some skeptics have questioned the conclusions.

The new report, the 20th in a series, focuses only on global warming and does not specify a cause.

"The evidence in this report would say unequivocally yes, there is no doubt," that the Earth is warming, said Tom Karl, the transitional director of the planned NOAA Climate Service.

Deke Arndt, chief of the Climate Monitoring Branch at the National Climatic Data Center, noted that the 1980s was the warmest decade up to that point, but each year in the 1990s was warmer than the '80s average.

That makes the '90s the warmest decade, he said.

But each year in the 2000s has been warmer than the '90s average, so the first 10 years of the 2000s is now the warmest decade on record.

The new report noted that continuing warming will threaten coastal cities, infrastructure, water supply, health and agriculture.

"At first glance, the amount of increase each decade — about a fifth of a degree Fahrenheit — may seem small," the report said.

"But," it adds, "the temperature increase of about 1 degree Fahrenheit experienced during the past 50 years has already altered the planet. Glaciers and sea ice are melting, heavy rainfall is intensifying and heat waves are becoming more common and more intense."

Last month was the warmest June on record and this year has had the warmest average temperature for January-June since record keeping began, NOAA reported last week.

The new climate report, published as a supplement to the Bulletin of the American Meteorological Society, focused on 10 indicators of a warming world, seven which are increasing and three declining.

Rising over decades are average air temperature, the ratio of water vapor to air, ocean heat content, sea surface temperature, sea level, air temperature over the ocean and air temperature over land.

Indicators that are declining are snow cover, glaciers and sea ice.

The 10 were selected "because they were the most obviously related indicators of global temperature," explained Peter Thorne of the Cooperative Institute for Climate and Satellites, who helped develop the list when at the British weather service, known as the Met Office.

"What this data is doing is, it is screaming that the world is warming," Thorne concluded.

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