Research News

2005 Was Warmest Year in Over a Century

The year 2005 was the warmest year in over a century, according to NASA scientists studying temperature data from around the world.

Image displaying the five warmest years in the past century. Image to right: 2005 was the warmest year since the late 1800s, according to NASA scientists. 1998, 2002 and 2003 and 2004 followed as the next four warmest years. Credit: NASA

Climatologists at NASA's Goddard Institute for Space Studies (GISS) in New York City noted that the highest global annual average surface temperature in more than a century was recorded in their analysis for the 2005 calendar year.

Some other research groups that study climate change rank 2005 as the second warmest year, based on comparisons through November. The primary difference among the analyses, according to the NASA scientists, is the inclusion of the Arctic in the NASA analysis. Although there are few weather stations in the Arctic, the available data indicate that 2005 was unusually warm in the Arctic.

In order to figure out whether the Earth is cooling or warming, the scientists use temperature data from weather stations on land, satellite measurements of sea surface temperature since 1982, and data from ships for earlier years.

The upper graph shows global annual surface temperatures relative to 1951 Image to left: The upper graph shows global annual surface temperatures relative to 1951 through 1980 mean based on surface air measurements at meteorological stations and ship and satellite measurements for sea surface temperatures. The dot at the top left corner shows that over the past 30 years, the Earth has warmed by 0.6°C or 1.08°F. The lower image is a colorful global map of temperatures averaged from 2005. Areas that have warmed the most are in red, areas that have cooled are in blue. Note that the Arctic has warmed significantly. These temperatures are from Dec. 2004 through Nov. 2005. Credit: NASA

Previously, the warmest year of the century was 1998, when a strong El Niño, a warm water event in the eastern Pacific Ocean, added warmth to global temperatures. However, what's significant, regardless of whether 2005 is first or second warmest, is that global warmth has returned to about the level of 1998 without the help of an El Niño.

The result indicates that a strong underlying warming trend is continuing. Global warming since the middle 1970s is now about 0.6° Celsius (C) or about 1° Fahrenheit (F). Total warming in the past century is about 0.8°C or about 1.4°F.

"The five warmest years over the last century occurred in the last eight years," said James Hansen, director of NASA GISS. They stack up as follows: the warmest was 2005, then 1998, 2002, 2003 and 2004.

Thumbnail of the first frame of the animation of the 10 year graph. Image/animation to right: The animation to the right shows a basic demonstration of the increase in annual mean temperature in ten year increments from 1891 through 1996. Warmest temperatures are in red. Click on image to view animation. Credit: NASA/GISS

Over the past 30 years, the Earth has warmed by 0.6°C or 1.08°F. Over the past 100 years, it has warmed by 0.8°C or 1.44°F.

Current warmth seems to be occurring nearly everywhere at the same time and is largest at high latitudes in the Northern Hemisphere. Over the last 50 years, the largest annual and seasonal warmings have occurred in Alaska, Siberia and the Antarctic Peninsula. Most ocean areas have warmed. Because these areas are remote and far away from major cities, it is clear to climatologists that the warming is not due to the influence of pollution from urban areas.

This graph shows temperature changes since 1950 for both the entire world and just for the low latitudes.

Image above: This graph shows temperature changes since 1950 for both the entire world and just for the low latitudes (23.6° North to South). Since 1950, world temperatures rose by 0.6°C (1.08°F) while the low latitude temperatures rose by 0.4°C (0.72°F). Blue semi-circles mark La Niñas, red rectangles mark El Niños, and green triangles mark large volcanoes. Credit: NASA

Also See

GISS Data Update: Global Temperature Trends: 2005 Summation

Media Contact

Leslie McCarthy, NASA Goddard Institute for Space Studies, New York, N.Y., 212-678-5507, leslie.m.mccarthy@nasa.gov