Blog Action Day 2009: Climate Change

When I signed up to participate in Blog Action Day 2009, I didn't realize how crazy busy my month would become.  Fortunately, the topic is one that I revisit periodically on this blog so I won't have to start from scratch.

When last I discussed why we all need the polar ice caps, I don't think I was very coherent.  So I will try again.

I need to get one more thing off my chest before I can breathe deeply and go to sleep. This morning, I heard a woman on the radio talking to someone who referred to the "global warming hoax". She countered that the polar ice caps are melting. The man asked who cares?

She could only mumble something about how she supposes the polar bears care.

Big sigh. It is clear that scientists are not getting through to the media. Let me try to explain why we all need the polar ice cap if we plan on continuing to live on this planet.

When the sun beats down on my dark hair, I put on a light colored hat.  The hat reflects the sun's heat and keeps me cooler.  Polar ice caps perform the same function, but on a planetary scale.  Without it, we are all gonna fry.  Is that clear enough?

Then I droned on about the planetary radiative budget--the balance of energy in and energy out.  Read the entire earlier post.  Explore all the links.  I will wait.

The main point I was trying to make was that the earth's surface reflects about 10% of the solar radiation back into space, mainly from high-albedo (fancy term for very reflective) regions.  Ice is about as reflective as it gets.

Moreover, the earth's axis is tilted and the summer pole's ice cap represents a large portion of the earth's surface that is exposed to the sun.  It performs the very important role of planetary sun hat.  That's why scientists wring our hands and drone on and on about the decline in the areal extent of the polar ice caps during the summer season.

Anyway, the mainstream media is still missing the big picture.  How many headlines have you read exclaiming that the polar ice cap is growing?  Global warming has been reversed.  Hallelujah!

If only it were that easy. 

The National Snow and Ice Data Center has posted a very nice explanation about why it is too early to rejoice, Arctic sea ice extent remains low; 2009 sees third-lowest mark.

At the end of the Arctic summer, more ice cover remained this year than during the previous record-setting low years of 2007 and 2008. However, sea ice has not recovered to previous levels. September sea ice extent was the third lowest since the start of satellite records in 1979, and the past five years have seen the five lowest ice extents in the satellite record.

We've only had polar weather satellites for about 50 years, but this is still deeply disturbing because of Milankovitch Cycles and Glaciation*.

The news becomes even worse.  Not all ice cover is created equal.   Thinner ice is more likely to melt completely in the summer.  Thicker ice gives more climate insurance; it gives us that extra margin of safety.

The ice cover remained thin, leaving the ice cover vulnerable to melt in coming summers. Scientists use satellites to measure ice age, a proxy for ice thickness. This year, younger (less than one year old), thinner ice, which is more vulnerable to melt, accounted for 49 percent of the ice cover at the end of summer. Second-year ice made up 32 percent, compared to 21 percent in 2007 and 9 percent in 2008 (Figure 5). Only 19 percent of the ice cover was over 2 years old, the least in the satellite record and far below the 1981-2000 average of 52 percent. Earlier this summer, NASA researcher Ron Kwok and colleagues from the University of Washington in Seattle published satellite data showing that ice thickness declined by 0.68 meters (2.2 feet) between 2004 and 2008.

* Milankovitch was a mathematician who theorized that the precession (wobbles) of the earth's spin are related to the periodic ice ages.  This graph from the third edition of Global Warming: The Complete Briefing by John Houghton, was my wake up call.

As the earth's spin axis wobbles, the amount of summer sunshine we get varies.  In the last 600,000 years, every orbit wobble that results in a decrease in summer sunshine has been  associated with growth in ice volume EXCEPT in the last 150 years.  What happened 150 years ago?  We ramped up our consumption of fossil fuels and started to pump ever increasing amounts of CO₂ and other greenhouse gases into the atmosphere.

Links:

• In February, I wrote about climate change and Ocean Acidification.
• My Blog Action Day 2007 post, Walking My Watershed.
• Arctic sea ice extent remains low; 2009 sees third-lowest mark
• IPCC
• Information about the Earth's Radiation Budget
• More details and a good explanation about the lower atmosphere radiation budget (I stole the top graphic from there and they, in turn, took it from the IPCC.)
• Arctic Melt Unnerves the Experts
• Sea Ice in Retreat web widget
• Click on the Cloud Cover tab; we can discuss the significance later.