I’ve already blogged about the record Arctic sea ice melt. The following picture and video further illustrate the point. This graphic from the Australian Conservation Foundation shows what the Arctic melt would look like if Australia was melting:
Note that Arctic sea ice volume has declined even more dramatically, with four-fifths disappearing in the 34-year record.
This video from The Yale Forum on Climate Change & The Media also explains it well:
The news that Arctic sea ice is in meltdown is being treated as merely one news item among many, even though it threatens to set off a chain of tipping points affecting all of humanity and life on Earth. I’m reminded of how the iceberg warnings sent to the Titanic by other ships were interspersed with passenger messages, and the final and most urgent warning was not considered important enough to deliver to the captain. In 1912 it was the presence of Arctic ice that failed to sink in; in 2012 it is the absence thereof; but the lack of needed attention is the same.
After a spectacular melt season, the Arctic sea ice finally appears to have reached its annual minimum on 16 September. In a horrible milestone, the ice extent shrank to just 3.4 million square km, which is three-quarters of a million square km (or 18%) below the 2007 record low broken in late August, and less than half of the 1980s average. (Note that sea ice extent includes areas with only partial ice cover; actual sea ice area got as low as 2.2 million square km.)
Source: International Arctic Research Center
The ice has retreated so far as to make the Arctic Ocean circumnavigable:
Source: National Snow & Ice Data Center (NSIDC) Read the rest of this entry ?
Source: International Arctic Research Center
As Australian politicians fiddle with the details of an extremely insufficient climate change policy, I’ve been watching Arctic sea ice news with increasing dismay. Summer sea ice in the Arctic is fast melting away, accelerated by amplifying feedbacks in what has been called a “death spiral”. The disappearance of Arctic summer sea ice is a key tipping point.
Sea ice floats on the ocean surface and is not to be confused with ice sheets on land. Arctic sea ice grows and shrinks seasonally, with an annual minimum in September. This year, eight independent datasets show we’ve already reached record low sea ice cover in the last week or so, with still weeks to go before the annual minimum.
In the IJIS Arctic sea ice extent dataset (pictured above), the previous record was 4.3 million square km on 24 September 2007 (with the 2011 minimum not far behind). This year we’re only up to 29 August, yet extent has already plummeted to 3.9 million square km. As if that’s not astonishing enough, the ice continues to shrink by 100,000 square km per day. Normally at this time of year, melting slows down as the melt season draws to a close – but this time it seems to be still accelerating, which is unprecedented in decades of observations. Nobody can predict what will happen next. Read the rest of this entry ?
I wrote this post for Skeptical Science.
At the recent US House of Representatives Committee on Science Space and Technology climate hearing, the Republicans called Dr. John Christy as an expert witness testifying against the global warming consensus. Unfortunately, Christy spent his time repeating a long list of climate myths, including the common contrarian refrain that “climate model output does not match up to the real world”. Let’s examine this claim.
Surface temperature observations are well within the range of model projections:
I wrote this post for Skeptical Science as a basic rebuttal of the argument “Ice isn’t melting”.
Contrary to contrarian claims, ice is melting at accelerating rates in the Arctic, Antarctica, Greenland, and glaciers all over the world. Arctic sea ice has shrunk by an area equal to Western Australia, and could be all gone in a decade.
Ice sheets are beginning to shrink
An ice sheet is a huge layer of land ice. The only ice sheets are in Antarctica and Greenland.
The Greenland ice sheet is losing mass at an accelerating rate. In recent years the ice loss has spread from the south coast around to the northwest.
Last year’s global temperatures are in, and the result is that 2010 is statistically tied with 2005 for the title of the warmest year since records began in 1880.
According to the US National Oceanic and Atmospheric Administration’s National Climatic Data Center (NOAA NCDC), the global temperature for both years was 0.62°C above the 20th-century average 13.9°C; 2010 came second by a thousandth of a degree. (Climatologists usually give temperatures as anomalies relative to an average, because they are easier to compare than absolute temperatures. The last month with a temperature below average was February 1985.)
2010 set new records for the warmest March, April, May, and June. Indeed, when the seasonal cycle is removed March 2010 was the third warmest month of all time (April, May, and November 2010 were also among the top 20). The ten warmest years according to NCDC are 2005/2010, 1998, 2003/2002, 2006/2009, 2007, 2004, and 2001. The 15 warmest years have all occurred since 1995; every year since 1976 has been above average. The 2000s are the warmest decade on record, followed by the 1990s and 1980s.
2010 was the Northern Hemisphere’s warmest year and the Southern Hemisphere’s sixth warmest. The former had its warmest April, May, June, July, August, and November in 2010, while the latter had its warmest February. There was particularly strong warmth in Greenland, Canada, northern Africa, and the Middle East; as well as warmer than average temperatures in southern Africa, eastern Europe, eastern Russia, and southern Asia; and cooler than average temperatures in central Russia and northern Europe. Except for the eastern Pacific, most of the oceans were warmer than average; the North Atlantic was particularly warm.
Source: NOAA National Climatic Data Center
I wrote this post for Skeptical Science as part of an ongoing series looking at the arguments made by Christopher Monckton against climate science.
This post examines Monckton’s arguments about global sea ice. Monckton claims:
[T]he global sea ice record shows virtually no change throughout the past 30 years, because the quite rapid loss of Arctic sea ice since the satellites were watching has been matched by a near-equally rapid gain of Antarctic sea ice.
Have Arctic ice losses truly been balanced by Antarctic gains? The first point to clarify is that we are talking about floating sea ice, not to be confused with land ice. Land ice at both poles and in glaciers around the world is sliding into the ocean at an accelerating rate. This net loss of land ice is contributing to sea level rise.
However, Monckton is clearly referring to sea ice. The rapid decline of Arctic sea ice has indeed coincided with an increase in Antarctic sea ice. But do these two opposite trends cancel out as Monckton suggests? In reality, the upward Antarctic trend is only slight compared to the plummeting Arctic trend. Tamino has crunched the numbers and found the Arctic trend is in fact more than three times faster than the Antarctic one. The net result is a statistically significant global decrease of more than a million km2 – would you agree with Monckton that this is “virtually no change”?
Figure 1: Global sea ice extent since 1979. (Image source: Tamino. Data is from US National Snow and Ice Data Center.) Read the rest of this entry ?
This post was written for Skeptical Science as a “basic rebuttal” to the argument “Southern sea ice is increasing”.
Sea ice around Antarctica has increased over the few decades that satellites have been measuring sea ice extent. First of all, it’s worth remembering that sea ice is not to be confused with land ice. This distinction might seem obvious, but the two are often confused in media reports. Sea ice is frozen seawater floating on the surface, whereas land ice is a layer of snow that has accumulated over time on a landmass. Antarctica is losing land ice at an accelerating rate.
However, it is clear that the extent of sea ice around the coast of the continent is growing. Why? The first explanation which comes to mind is that the Southern Ocean must be cooling. But on the contrary, the Southern Ocean has warmed by around 0.5°C in the three decades since satellites began measuring sea ice trends.
The true reasons for the increasing ice are a complex set of factors. One factor is an increase in precipitation over the Southern Ocean, which means more snowfall. However, this trend is expected to reverse in coming decades as the Antarctic continues to warm.
Finally, southern sea ice is not particularly important to the climate. Unlike land ice, sea ice doesn’t affect sea levels because it’s already displacing water. And unlike the situation in the Arctic, where disappearing sea ice is making the Arctic Ocean less reflective and amplifying Arctic warming, a decline in southern sea ice would not warm the Antarctic climate. For as long as climatologists have studied it, the Southern Ocean has been almost ice-free in summer, the time of year when it would receive enough heat from the Sun to have a large effect. The issue of southern sea ice is really just a distraction which diverts our attention from the more important issue of sea ice melt in the Arctic.
In conclusion, the increase of southern sea ice does not contradict global warming. The Southern Ocean is in fact warming, the increase of sea ice is due to a variety of factors, and sea ice is not as important to the Antarctic climate as it is to the Arctic.
In 2007, the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) concluded that global warming is unequivocal, and that serious impacts of global warming are already beginning to occur. The AR5 isn’t due until 2013, but in 2009, a non-IPCC report called the Copenhagen Diagnosis was released to provide an update on the AR4. The authors found more evidence that various impacts were occurring, many of them at an increasing rate.
This is the third in a series of posts on the arguments contrarians make against global warming. In Part 1, I discussed whether the global temperature had increased (short answer: yes). In Part 2, I discussed whether it had recently stopped increasing (short answer: probably not). I know I promised a post about the hockey stick, but that is turning out to be more difficult to write about than I thought it would be; so in the meantime, here is a piece about one impact of global warming.
Claim: Ice sheets, glaciers, and sea ice are not melting.
Fact: All of the above are melting.
The Gravity Recovery and Climate Experiment (GRACE) satellites, launched in 2002, are able to measure gravity so sensitively they can detect changes in the mass of ice sheets (huge layers of land ice). GRACE measurements show that since 2002, the Antarctic ice sheet has been losing mass at an accelerating rate.
Antarctica has been losing 190 Gt/yr of ice since 2002. (Source: NASA)
Precarious Climate 
