to support Skeptical Science
iPhone app Download	Android app Download
Nokia app Download

	It's the sun
	Climate's changed before
	There is no consensus
	It's cooling
	Models are unreliable
	Temp record is unreliable
	It hasn't warmed since 1998
	Ice age predicted in the 70s
	We're heading into an ice age
	Antarctica is gaining ice
	View All Arguments...

Latest Posts

• Climate change: Water vapor makes for a wet argument
• Carbon dioxide equivalents
• How we know an ice age isn't just around the corner
• Urban Heat Islands: serious problem or holiday destination for skeptics?
• The surprising result when you compare bad weather stations to good stations
• The empirical evidence that humans are causing global warming
• Sea level rise: the broader picture
• Human CO2: Peddling Myths About The Carbon Cycle
• Why we can trust the surface temperature record
• Ocean acidification threatens entire marine food chains
• Comparing volcanic CO2 to human CO2
• Can humans affect global climate?
• Climate Models: Learning From History Rather Than Repeating It
• Arctic sea ice... take 2
• Hansen etal hit a Climate Home Run -- in 1981
• Station drop-off: How many thermometers do you need to take a temperature?
• Arctic Sea Ice: Why Do Skeptics Think in Only Two Dimensions?
• Pakistan flood: many more will die unless more aid is delivered quickly
• Medieval Warm Period: rhetoric vs science
• Weather vs Climate: Watch the waves, miss the turning of the tides
• University of Western Australia Open Day 2010
• The main culprit in mid-century cooling
• Dust-Up On Mars: Should Martians Be Sceptical of Global Warming?
• What caused early 20th Century warming?
• The Oregon Petition: How Many Scientists Does It Take To Change A Consensus?
• How climate skeptics misunderstand past climate change
• 1934: the 47th hottest year on record
• The Strange Case of Albert Gore, Inconvenient Truths and a Man in a Powdered Wig
• What were climate scientists predicting in the 1970s?
• Can't We At Least Agree That There Is No Consensus?

Archives

Ice isn't melting

What the science says...

Figure 1 shows gravity satellite measurements of Greenland ice mass from April 2002 to February 2009 (Velicogna 2009). The blue line/crosses show monthly values of ice mass. The red crosses have seasonal variability removed. The green line is the best fitting quadratic trend. The best fitting trend finds that Greenland ice loss is accelerating at a rate of 30 Gigatonnes/yr². Greenland's mass loss doubled over the 9 year period. More on Greenland...

Figure 2: Time series of ice mass changes for the Greenland ice sheet estimated from GRACE monthly mass solutions for the period from April 2002 to February 2009. Unfiltered data are blue crosses. Data filtered for the seasonal dependence using a 13-month window are shown as red crosses. The best-fitting quadratic trend is shown (green line). (Velicogna 2009)

Figure 2 shows gravity measurements of land ice mass changes in Antarctica for the period April 2002 to February 2009 (Velicogna 2009) . The blue line/crosses show the unfiltered, monthly values. The red crosses have seasonal variability removed. The green line is the best fitting trend. Ice loss is accelerating at a rate of 26 Gigatonnes/yr². The Antarctic ice sheet plays an important role in the total contribution to sea level. That contribution is continuously and rapidly growing.

Figure 2: Ice mass changes for the Antarctic ice sheet from April 2002 to February 2009. Unfiltered data are blue crosses. Data filtered for the seasonal dependence are red crosses. The best-fitting quadratic trend is shown as the green line (Velicogna 2009).

Globally, glaciers are shrinking in area and thickness and the melt rate has accelerated dramatically since the mid-1990s. The National Snow and Ice Data Center have calculated global change in glacier volume - their results show glaciers are shrinking at an alarming rate. More on glaciers... 

Figure 3: Annual change in global glacier thickness (left axis, meters of water equivalent, m/yr) and cumulative value (right axis, m), based on surface area-weighted mass balance observations. Dates of major volcanic eruptions are shown, since stratospheric aerosols have a cooling effect on climate. Red arrow highlights volume rate change (source: NSIDC) .

Global warming has a clearly observed, long term effect on Arctic sea ice. In fact, although climate models predict that Arctic sea ice will decline in response to greenhouse gas increases, the current pace of retreat at the end of the melt season is exceeding the models’ forecasts by around a factor of 3 (Stroeve 2007). More on Arctic ice...

Figure 4: September Arctic Sea Ice Extent (thin, light blue) with long term trend (thick, dark blue). Sea ice extent is defined as the surface area enclosed by the sea ice edge (where sea ice concentration falls below 15%).

The one exception to this pattern of accelerating ice loss is Antarctic sea ice which has shown long term growth since satellites began measurements in 1979. This is despite the fact that the Southern Ocean has been warming faster than the rest of the world's oceans. Globally from 1955 to 1995, ocean have been warming at 0.1°C per decade. In contrast, the Southern Ocean has been warming at 0.17°C per decade. Not only is the Southern Ocean warming, it is warming faster than the global trend.

If the Southern Ocean is warming, why is Antarctic sea ice increasing? There are several contributing factors. The hole in the ozone layer above the South Pole strengthens cyclonic winds that circle the Antarctic continent. The wind pushes sea ice around, creating areas of open water known as polynyas. More polynyas leads to increased sea ice production. Another contributor is changes in ocean circulation which cause less heat is transported upwards from the deeper, warmer layer. Hence less sea ice is melted.

Figure 5: Surface air temperature over the ice-covered areas of the Southern Ocean (top). Sea ice extent, observed by satellite (bottom). (Zhang 2007)

Printable Version  |  Link to this page

Link to this page