Garbage is Forever

Some garbage never dies.

A comment on a recent post consisted solely of this link:

Polar Ice

One of the results of global warming is melting of the polar ice cap. The north pole is expected to be ice-free during summer as early as 2030 — even earlier by some accounts. In part this is due to the phenomenon of “polar amplification.” Global warming has hit the arctic harder than the rest of the globe; the rate of warming there is more than double the global rate. As a result, the polar ice cap is melting — rapidly. In fact, arctic sea ice extent is at an all-time low. Here’s the latest graph (you can view this, and others, at cryosphere today).

Video on YouTube

This is a little different from the usual post; it’s not about the science. I happened accross an interesting video on YouTube. It discusses an argument I’ve heard before; it’s basically the “better safe than sorry” argument, but stated in a compelling way. And it’s less than 10 minutes of your time.

Opinions?

UPDATE UPDATE UPDATE

The creator of the video has added some follow-ups in response to some of the many responses he’s received. You can view then conveniently here, or on the creator’s YouTube site here.

They’re nothing if not entertaining. And in my opinion, his analysis is spot on.

Hemispheres

Throughout the 20th century, global average temperature shows an interesting evolution. From about 1915 to about 1944, temperature rose. Then from about 1944 to 1951, global temperature declined. It remained roughly constant from about 1951 to about 1975, and since then it has risen sharply.

People often wonder why the planet didn’t warm from 1944 to 1975. Denialists often say that the planet actually cooled for 30 years or more, but this is simply not so; the cooling was confined to a brief period (about 1944 to 1951), followed by relative stability for several decades. But the question remains, with man-made CO₂ (and other greenhouse gases) in the atmosphere, why did the planet not warm for several decades mid-century?

Impure Speculation

Recent computer simulations at HadCRU have led to media announcements that global warming will remain “levelled off” until 2009, at which point it will take off like a bat out of hell. The folks at HadCRU know a lot more about the climate system than I do, and their computer models are probably very good. But I admit, I’m skeptical about their forecast.

It’s not the long-term aspect of the forecast I’m suspicious of. The ability of computer models to make successful long-term forecasts has already been demonstrated: James Hansen’s team at NASA GISS forecast decade-scale increases in global temperature that have already come to pass. It’s the short-term aspect that troubles me. Long-term, climate follows known, and very basic, laws of physics: put more energy in, the temperature goes up. But short-term changes involve the details, not in the “big picture” but in the “small picture,” and often the devil is in the details. Also, there are known factors which are unpredictable, and would easily throw any short-term prediction out of whack. If there’s a strong, sustained el Nino in, say, 2008, global temperature won’t “remain levelled off,” 2008 will break the record. If there’s a massive volcanic eruption in 2008, global temperature will take a nose-dive as the planet cools for a couple of years.

So I read the actual paper containing the new predictions. It turns out that the press reports are considerably overblown (surprise!); they give the unmistakeable impression that the HadCRU team has made definitive predictions of the future progress of global warming over the next decade or so, as though we now know with confidence how global average temperature will evolve up to 2014. If you read the actual paper you’ll find that is simply not so. The researchers do claim that their new model, DePreSys (“Decadal Climate Prediction System”) performs demonstrably better at short-term prediction than previous models (which they simulate using a system they call NoAssim), and in fact it does. Comparison between hindcasts from the models (using past data to “predict” what follows in the historical record) clearly demonstrates significant improvement in the predictive ability of the DePreSys model. But it does not demonstrate, nor do the authors claim, the ability to make ironclad predictions.

Before and After

The global-warming-denialist blogosphere is aflutter. News of the recent correction to USHCN temperature data has caused them to declare that global warming no longer exists, that 1998 or 2005 is no longer the hottest year on record (it’s now 1934), and that global warming is a “Y2K bug.” For example, budsimmons gleefully asks, “Lets see if Al Gore revises his road show.”

The recently-discovered corrections apply only to some stations in the U.S., and the claim that “1934 is now the hottest year on record” applies only to the lower 48 states of the continental U.S. Before the recent correction, for the lower-48 U.S. states the years 1998 and 1934 were too close to call — a “statistical tie” — with 1998 having the slightly higher numerical value. After the recent correction, for the lower-48 U.S. states the years 1998 and 1934 are too close to call — a “statistical tie” — with 1934 having the slightly higher numerical value.

Yet most denialist bloggers simply state that 1934 is now the hottest year on record — with no qualification given that this applies to the lower-48 U.S. states, not to the globe. The lower-48 of the U.S. make up less than 2% of the area of the globe. What is the impact on global average temperature? What’s the hottest year on record — globally — after the correction? Let’s take a look.

North Atlantic Storms (NATL TC)

A new paper by Holland & Webster has been accepted for publication in Philosophical Transactions of the Royal Society A, on the statistics of tropical cyclones in the North Atlantic basin. The gist of the paper is well summarized in the opening sentences of the abstract:

We find that long-period variations tropical cyclone and hurricane frequency over the past century in the North Atlantic Ocean has occurred as three, relatively stable regimes separated by sharp transitions. Each regime has seen 50% more cyclones and hurricanes than the previous one and is associated with a distinct range of sea surface temperatures (SSTs) in the eastern Atlantic Ocean. Overall, there has been a substantial 100-year trend leading to related increases of over 0.7oC in SST and over 100% in tropical cyclone and hurricane numbers. It is concluded that the overall trend in SSTs and tropical cyclone and hurricane numbers is substantially influenced by greenhouse warming.