I’ve found the global warming/climate change debate to be frustrating.  The Earth is too large a system to grasp intuitively.  In such a large system, anyone can “cherry-pick” a small subset of data to illustrate any point.  Many discussions seem to distill down to:  “You’re lying!”

I posted on the social aspects of the debate previously.  Today I will discuss the science of global warming and climate change.  (“Global warming” refers to average global temperatures while “climate change” refers to the effects.)

Global warming is complex enough to make my eyes cross.  It involves many parameters that must be examined over decades and preferably centuries.  I will primarily use information from http://www.skepticalscience.com/.  This site provides the largest and most accessible collection of responses to global warming objections I’ve found.  SkepticalScience has a handy glossary with mouse-over pop-ups in the text.  For example, ice sheets, ice shelves, glaciers, and sea ice are different things.  While unabashedly defending mainstream climate science against “climate myths”, the site also provides a more exhaustive list of objections than anywhere else I’ve run across: 174 of them!  There are also comments from pro and con readers.

I leave you to explore as many of the 174 objections as interest you.  Here is a sampling.

Objection: Arctic sea ice has recovered.

Arctic sea ice, the “canary in the global warming coal mine,” is a particularly interesting topic.  SkepticalScience has several pages that apply.  Direct measurements via satellite have only been available since 1979, though there are clues to the past such as ocean sediment cores.  Sea ice shows large seasonal variations (with an annual minimum in September) and the extent of the ice is strongly affected by weather.  In 2010, for example, sea ice extent recovered dramatically in March, only to melt again by May.

Longer duration variations also occur.  “It’s true that natural variations of the climate have caused significant changes in Arctic ice extent… The Arctic appears to have undergone an unusually cool period in the early 19th century, certainly natural, with recovery to more normal conditions extending into the 20th century.”  SkepticalScience.

Ice reflects sunlight, which impacts the Earth’s overall “albedo”; an increased albedo would contribute to cooling.  As SkepticalScience says, “albedo is a subject needing a lot more research.  It’s an important feature of our climate, and a complex one.  It is not yet possible to make definitive statements about what the future may hold.  In fact, it is a good example of the ‘unsettled’ nature of climate change science.”

My Comment:  Despite the uncertainty, the importance of the arctic to understanding climate and to commercial enterprises such as shipping and undersea mining makes it worth discussing.  I appreciate SkepticalScience acknowledging the uncertainties, and I note their conclusion:  “It is clear from the various data sets, terrestrial and satellite, that both the sea ice extent and multi-year ice volume are reducing.  Sea ice extent recovered slightly during the Arctic winters of 2008-09, but the full extent of annual ice reduction or gain is seen in September of each year, at the end of the Arctic summer. The volume of multi-year ice has not recovered at all, and is showing a steeply negative trend.”

Objection:  Global warming is not bad.

Excerpt from SkepticalScience Response:  “While CO₂ is essential for plant growth, all agriculture depends also on steady water supplies… It has been suggested that higher latitudes – Siberia, for example – may become productive due to global warming, but the soil in Arctic and bordering territories is very poor, and the amount of sunlight reaching the ground in summer will not change because it is governed by the tilt of the earth….

The opening of a year-round ice free Arctic passage between the Atlantic and Pacific oceans would confer some commercial benefits…

Positive effects of climate change may include greener rainforests and enhanced plant growth in the Amazon, increased vegetation in northern latitudes and possible increases in plankton biomass in some parts of the ocean…”

My Comment: I can accept that focusing on a single parameter is misleading.  There are likely to be some “winners” in a warmer world, but also “losers.”  I am an American and America is a “winner” in the current world.  Sorry to be self-centered, but change may be bad for me.

Objection: Temperature increases have stopped.

From SkepticalScience Response: The gif chart presented to show temperature continues to increase has become somewhat famous.  I’ve inserted a screen-capture of the chart above, at right.  It shows an overall upward trend in temperatures with several plateaus along the way.  You can view the gif chart here.

Another response:  This op-ed by Dr. Peter Gleick is a must-read.  He is quite adamant and the article goes on to support his statements with data (for example, the chart below, at right):

“These statements [that global warming has stopped] are scurrilous deceptions and falsehoods. The planet is warming – an observation noted by every climate research institution tracking temperatures, the US National Academy of Sciences (over and over and over), every other national academy of sciences on the planet, and every professional society in the geosciences.”

My Comment:  I’ve worked with large sets of data myself (not related to climate).  It seems entirely reasonable to me that a trend measured over decades in a complex system will show ups and downs, and that comparing a couple local maximums can give a false impression of stasis.

Objection:  There is no consensus.

I have often failed to describe to friends the type of consensus that is meant by “warmers”.  If there is obviously discord and disagreement, what is meant by consensus?  Here is a fine description from a self-proclaimed “denier” turned “warmer”:

“Don’t confuse consensus with consensus. This one had me confused for a long time. Like the word theory, which has a drastically different meaning in science than it does in the vernacular, consensus can mean two very different things. In politics a consensus is an aggregate expression of opinion.  It’s only as valid as the majority agrees it is. In science it is a description of where the science has led… [T]he consensus is not what gives power to the conclusion, the science leads to the conclusion.”  http://skeptoid.com/blog/2011/06/15/i-global-warming-skeptic/  The entire post is excellent, with advice for left and right-leaning readers.

Excerpt from SkepticalScience Response: “In the scientific field of climate studies… the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them. A survey of 928 peer-reviewed abstracts on the subject ‘global climate change’ published between 1993 and 2003 shows that not a single paper rejected the consensus position that global warming is man caused (Oreskes 2004).”

My Comment: I included a lot of words about consensus because it is very important to my thinking.  A bumper-sticker doesn’t cut it here – I must say “consensus in the scientific, peer-reviewed climate-science literature”.  I don’t think I’ve read any significant disagreement with the SkepticalScience response.

Those who object to the “warmers” consensus statement publish lists of people who disagree with the scientific consensus, but do not dispute that the published, peer-reviewed literature is overwhelmingly in agreement on global warming.  The only counter response I’ve seen is a conspiracy theory: Scientists are too scared of authority or too corrupted by research grant money to oppose the mainstream theory of global warming.  I have worked in a scientific field (though not in the climate sciences).  In my experience, most scientists would love to overturn an established theory.  It would make their careers.  I would have to see strong evidence that a conspiracy has controlled climate scientists world-wide for decades.  I have not seen such evidence.

In summary:

I am not an expert in climate science and never will be.  This is true about most scientific topics.  What can a reasonable person do?

I follow a simple heuristic:  Accept what the science says when the experts mostly-all agree.  I realize experts change their minds and I’m alert for updates in areas that interest me.  Headlines can be misleading, so I try to learn about the details.

I accept:  The Earth is warming and climate is changing in response.  Human activities, including fossil fuel burning and land use practices, are forcing a change unprecedented in civilization’s history.  This will lead to negative impacts on ecosystems and people in many ways.

I believe:  Everyone in the world deserves a chance to prosper the way America prospers, and that Americans deserve to continue to prosper, too.  “You are a child of the Universe, no less than the trees and the stars.  You have a right to be here.”  [Desiderata]

Population growth in wealthy countries is dropping, so encouraging all countries in the world to prosper may be the best win-win tactic we have.  It is ironic if the prosperity some Environmentalists tell us we must abandon may actually “save the world.”  How decreased populations will sort out economically I can’t tell: our current model of prosperity depends on population growth, and my crystal ball is cracked and cloudy.

I have faith:  We can make decisions today that reduce the pain along the way.  I see ways we can adapt to specific impacts of climate change, and ways to slow the release of CO₂ and other greenhouse gases.  Ironically, recent increases in natural gas production are reducing carbon emissions from coal because the free market favors gas, not because of any ideology.  We need more improvements like that.  Future generations will grapple with these issues and come out ahead.