Weatherdem's Weblog

Bridging climate science, citizens, and policy


5 Comments

How the IPCC Underestimated Climate Change – Scientific American article

Scientific American published an article summarizing what I’ve written about for a couple of years: the IPCC’s projections aren’t 100% correct.  Gasp – the horror!  But, contrary to what skeptics think, the direction the IPCC’s reports were wrong are opposite of what they claim.  The projections time and again underestimated future changes.  I think a valid complaint, and one I’ve made many times myself, is that the IPCC process is too conservative – it takes too long to get the kind of consensus they’re looking for.  Rapidly changing conditions are not well handled by the IPCC process.  When there is conflicting evidence of something, the IPCC has tended to say nothing in an effort not to upset anybody.  The good news is there are indications this is changing.  The list:

1. Emissions

This is the biggest one.  Too many studies focused on moderate emission pathways, when yearly updates showed our actual emissions were on the high range of those considered by the IPCC.  I actually posted on this two days ago: CO2 Emissions Continue to Track At Top of IPCC Range.  This has implications for every other process that follows.

2. Temperature

More accurately, energy in the climate system is the variable of interest.  It is easy to point out that temperatures since 2000 haven’t increased as much as projected.  It is also easy to compare observed trends since 1980 and claim AR4 models over-predicted temperature rise.  This conflates a couple of issues: the AR4 wasn’t used to project since 1980.  More importantly, the difference between observed trends since 1980 and projected temperatures from half of the AR4 models was less than 0.04°C (0.072°F).  That’s pretty darned small.  With respect to the trend since 2000, the real issue is energy gain.  The vast majority of energy has accumulated in the oceans:

Photobucket

More specifically, if the heat is transported quickly to the deep ocean (>2000ft), the sea surface temperature doesn’t increase rapidly.  Nor does atmosphere or land temperatures change.  This is true at least in the short-term.  When the ocean transports this heat from the deep back to the surface, we should be able to more easily measure that heat.  Put simply, the temporary hiatus of temperature rise is just that: temporary.  Are we prepared for when that hiatus ends?

The relatively small increase in near-surface air and land temperatures is thus explained.  The IPCC never claimed the 4.3° to 11.5°F temperature rise (AR4 projection) would happen by 2020 – it is likely to happen by 2100.  Expect more synergy between projected temperatures and observed temperatures in the coming years.  Also remember that climate is made up of long-term weather observations.

Additionally, aerosols emitted by developing nations have been observed to reflect some of the incoming solar radiation back to space.  Once these aerosols precipitate out of the atmosphere or are not emitted at some point in the future, the absorption of longwave radiation by the remaining greenhouse gases will be more prominent.  The higher the concentration of gases, the more radiation will be absorbed and the faster the future temperature rise is likely to be.  These aerosols are thus masking the signal that would otherwise be measured if they weren’t present.

3. Arctic Meltdown

This is the big story of 2012.  The Arctic sea ice melted in summer 2012 to a new record low: an area the size of the United States melted this year!  Even as late as 2007 (prior to the previous record-low melt), the IPCC projected that Arctic ice wouldn’t decrease much until at least 2050.  Instead, we’re decades ahead of this projection – despite only a relatively small global temperature increase in the past 25 years (0.15°C or so).  What will happen when temperatures increase by multiple degrees Centigrade?

4. Ice sheets

These are the land-based sheets, which are melting up to 100 years faster than the IPCC’s first three reports.  2007’s report was the first to identify more rapid ice sheet melt.  The problem is complex cryospheric dynamics.  Understandably, the most remote and inhospitable regions on Earth are the least studied.  Duh.  That’s changing, with efforts like the fourth International Polar Year, the results of which are still being studied and published.  Needless to say, modern instrumentation and larger field campaigns have resulted in advances in polar knowledge.

5. Sea Level Rise

It’s nice being relevant.  I just posted something new on this yesterday: NOAA Sea-Level Rise Report Issued – Dec 2012.  The 3.3mm of sea-level rise per year is higher than the 2001 report’s projection of 2mm per year.  Integrated over 100 years, that 1mm difference results in 4″ more SLR.  But again, with emission and energy underestimates, the 3.3mm rate of SLR is expected to increase in future decades, according to the latest research.  Again, another mm per year results in another 4″ 100 years from now.  Factors affecting SLR that the IPCC didn’t address in 2007 includes global ocean warming (warmer water takes up more volume), faster ice sheet melt, and faster glacial melt.  Additionally, feedback mechanisms are still poorly understood and therefore not well represented in today’s state-of-the-art models.

6. Ocean Acidification

The first 3 IPCC reports didn’t even mention this effect.  In the past 250 years, ocean acidity has increased by 30% – not a trivial amount!  As the article points out, research on this didn’t even start until after 2000.

7. Thawing Tundra

Another area that is not well-studied and therefore not well understood.  The mechanics and processes need to be observed so they can be modeled more effectively.  1.5 trillion tons of carbon are locked away in the currently frozen tundra.  If these regions thaw, as is likely since the Arctic has observed the most warming to date, methane could be released to the atmosphere.  Since methane acts as a more efficient GHG over short time frames, this could accelerate short-term warming much more quickly than projected (See temperatures above).  The SciAm article points out the AR5, to be released next year, will once again not include projections on this topic.

8. Tipping Points

This is probably the most controversial aspect of this list.  Put simply, no one knows where potential tipping points exist, if they do at all.  The only way we’re likely to find out about tipping points is by looking in the past some day in the future.  By then, of course, moving back to other side of the tipping point will be all but impossible on any time-frame relevant to people alive then.

Summary

There are plenty of problems with the UNFCCC’s IPCC process.  Underestimation of critical variables is but one problem plaguing it.  Blame it on scientists who, by training, are very conservative in their projections and language.  They also didn’t think policymakers would fail to curtail greenhouse gas emissions.  Do policymakers relying on the IPCC projections know of and/or understand this nuance?  If not, how robust will their decisions be?  The IPCC process needs to be more transparent, including allowing more viewpoints to be expressed, say in an Appendix compendium.  The risks associated with underestimating future change are higher than the opposite.


Leave a comment

Climate-Related News 5/29/09

I’m going to talk about two news articles I saw this week.  The first is about Arctic methane concentration levels rising.  After 10 years of no change in concentration values, methane concentrations rose in 2007 and 2008 by 0.6% each year.  While that doesn’t sound like a lot, it is important to remember that methane is 25 times as effective a greenhouse gas as is carbon dioxide.  It therefore takes much less of a rise in concentration to effect the climate in the same way.  The biggest problem is that nobody knows for certain what the source of the new methane is.  Finding that out would give scientists a better idea of how much of an impact on the climate it is likely to have.

Carbon pollution is expected to rise by at least 40% worldwide by 2030 if emissions aren’t cut.  Most of the forecasted rise comes from the BRIC developing countries: Brazil, Russia, India and China.  Ways must be found to bring these countries into the 21st century, technologically and economically speaking, without endangering the planet.  It’s a fact that is acknowledged by climate scientists who are trying to bring increased focus to societal impacts due to climate change as part of the IPCC’s 5th Assessment Report, due to be issued in 2013.


1 Comment

2008 Temperatures, Atlantic Hurricane Season & More

I wanted to write a post about some datasets that encompass 2008 to put my recent discussions and future posts on climate in perspective.  First up, the World Meteorological Organization’s global temperature dataset.  In a preliminary report issued on 16 Dec, 2008’s global mean temperature was 14.3 °C, making it the 10th warmest year on record going back to 1850.  Despite a lingering La Nina, which is characterized by cooler than normal temperatures, 2008 was warmer than the 1990’s average temperature.  It was almost as warm as 1997, in the runup to the strongest El Nino on record.  It was only 0.2 °C cooler than the 1998 record temperature anomaly.  Those 10 warmest years on record?  All have occurred since 1997.

The La Nina that developed during 2007 and hung around through 2008 was easing back by the end of the year.  November was the 4th warmest all-time (land and ocean combined), as measured by NOAA’s National Climatic Data Center.

  • The November combined global land and ocean surface temperature was 1.06 degrees F (0.59 degree C) above the 20th century mean of 55.2 degrees F (12.9 degrees C).
  • Separately, the November 2008 global land surface temperature was fourth warmest on record and was 2.11 degrees F (1.17 degrees C) above the 20th century mean of 42.6 degrees F (5.9 degrees C).

How much did the La Nina affect global temperatures?  According to NASA, the 2008 meteorological year (Dec 2007 – Nov 2008) was the coolest year since 2000, yet was still the 9th warmest on record (dating back to 1880).  So the coolest year since 2000 is a good thing, right?  Well, until the La Nina subsides.  2003, 2005, 2006 and 2007 were as anomalously warm as the record 1998 year, which had an extreme El Nino event.  How anomalously warm will the next El Nino year be?

More importantly, the trend in the Met Office/WMO and the NASA data continue to show a large and rapidly increasing warm anomaly.  Of particuar worry is the very large warm anomaly found over the Antarctic peninsula and eastern Russia.  The former has seen massive ice sheet calving episodes in recent years and increased ice flow toward the ocean from land as a result.  The latter has seen increasing emissions of methane as the permafrost thaws.  The former will lead to rising sea levels if trends don’t change.  The latter will release a greenhouse gas 20x as effective as CO2 is in energy absorption.  There is a lot of methane trapped in the permafrost.  Thawing the permafrost could initiate a positive feedback loop in which even more methane is released from the ground, which would warm the region and the globe even more.

The above temperature record also occurred in a period of low solar activity, which many climate change deniers claim is the most important factor driving our climate.  Most climatologists acknowledge the sun’s activity as being one input into our climate system, but also recognize that human forcing has likely become a more important climate driver.

NOAA’s 2008 Atlantic Hurricane Report details some of the noteworthy accomplishments of the season:

  • Bertha was a tropical cyclone for 17 days (July 3-20), making it the longest-lived July storm on record in the Atlantic Basin.
  • Fay is the only storm on record to make landfall four times in the state of Florida, and to prompt tropical storm and hurricane watches and warnings for the state’s entire coastline (at various times during its August lifespan).
  • Paloma, reaching Category 4 status with top winds of 145 mph, is the second strongest November hurricane on record behind Lenny in 1999 with top winds of 155 mph).

More items of interest:

Overall, the season is tied as the fourth most active in terms of named storms (16) and major hurricanes (five), and is tied as the fifth most active in terms of hurricanes (eight) since 1944, which was the first year aircraft missions flew into tropical storms and hurricanes.

For the first time on record, six consecutive tropical cyclones (Dolly, Edouard, Fay, Gustav, Hanna and Ike) made landfall on the U.S. mainland and a record three major hurricanes (Gustav, Ike and Paloma) struck Cuba. This is also the first Atlantic season to have a major hurricane (Category 3) form in five consecutive months (July: Bertha, August: Gustav, September: Ike, October: Omar, November: Paloma).

Follow

Get every new post delivered to your Inbox.

Join 293 other followers