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 ?
Recent findings suggest climate change in Greenland may be approaching a tipping point, beyond which amplifying feedbacks could lead (probably over centuries) to complete melting of the ice sheet, raising sea level by about 7 meters.
In June, a team of glaciologists led by Jason Box predicted that we would see melting across 100% of the ice sheet’s surface area in summer within a decade. They drew that conclusion from data on the Greenland ice sheet’s surface reflectivity, or “albedo”, showing the surface has gotten darker over the last 12 years. A darker surface absorbs more heat, leading to more melting, causing albedo to decrease further, and so on in a vicious circle.
The ice naturally gets less reflective in summer because the shape of the snowflakes changes, but in 2012 Greenland has become much darker than in previous summers. This is occurring particularly at high elevations, which were previously too cold to melt and indeed had gained ice from increasing snowfall. This month, at the height of the melt season, Greenland’s albedo has fallen far off the charts:
Figure 1: Surface albedo of the Greenland ice sheet (average of all elevations) between March and October in each year from 2000 to 2012. (Source: Ohio State University) 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 “It’s not urgent”.
Global warming is an increasingly urgent problem. The urgency isn’t obvious because a large amount of warming is being delayed. But some of the latest research says if we want to keep the Earth’s climate within the range humans have experienced, we must leave nearly all the remaining fossil fuels in the ground. If we do not act now we could push the climate beyond tipping points, where the situation spirals out of our control. How do we know this? And what should we do about it? Read on.
James Hansen, NASA’s top climatologist and one of the first to warn greenhouse warming had been detected, set out to define dangerous human interference with climate. In 2008, his team came to the startling conclusion that the current level of atmospheric carbon dioxide (CO2) is already in the danger zone.
Since the Industrial Revolution, atmospheric CO2 has increased from 280 to 390 parts per million (ppm). Don’t be fooled by the small number – 390 ppm is higher than CO2 has been in millions of years. CO2 is rising by 2 ppm per year as we continue to burn fossil fuels. To stabilise the Earth’s climate, we must reduce CO2 to the relatively safe level of 350 ppm. And we must hurry, because the task will soon be an impossible one.
The 350 target is based not on climate modeling, but on past climate change (“paleoclimate”). Hansen looked at the highly accurate ice core record of the last few hundred thousand years, sediment core data going back 65 million years, and the changes currently unfolding. He discovered that, in the long term, climate is twice as sensitive in the real world as it is in the models used by the IPCC. Read the rest of this entry ?
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.
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.
So far in my series of posts on the arguments contrarians make against global warming, I’ve written about the changes being observed in the Earth’s climate. I wrote about whether the global temperature has increased (short answer: yes); whether it has recently stopped increasing (short answer: probably not); and whether ice is declining around the world (short answer: yes). Now I figure it’s time to go back to where it all begins: with CO2 and the greenhouse effect.
Claim: The greenhouse effect does not exist.
Fact: The greenhouse effect is as established a phenomenon as any. It was first discovered in the 1820s by French mathematician Joseph Fourier, and the basic physics was essentially understood by the 1950s. Greenhouse gases are completely transparent to visible light but less so to infrared. Visible sunlight is transmitted through the Earth’s atmosphere and warms the surface, causing Earth to emit infrared light (because Earth is much cooler than the Sun, its radiation peaks at a lower wavelength). But on the way out, some of this radiation is trapped by greenhouse gases, which reflect it back to Earth and make the surface warmer. If it were not for the greenhouse effect, the Earth’s average surface temperature would be about 33°C colder.
Claim: CO2 is not evil/not a pollutant.
Fact: The “straw person” fallacy is committed when one (intentionally or otherwise) misrepresents the argument one is attempting to counter. “CO2 is not evil” could be a textbook example. Of course there is nothing inherently evil about carbon dioxide — but nobody is claiming that there is. It’s just another molecule. Read the rest of this entry ?
Precarious Climate 
