Climate Emergency: Time to Slam on the Brakes

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.

A basic overview of melting ice around the globe

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.

Monckton Myth: Global Sea Ice

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.

Global Sea Ice Is Decreasing

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.)

Increasing southern sea ice

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.

Global Warming Contrarians Part 4: Back to Basics

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.

Global Warming Contrarians Part 3: Hiding the Decline of Ice

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)