If you’re an American who follows the news, you know that it’s been all midterm elections, all the time over the past few days.  And that’s great: this was a major election and it’s encouraging to see citizens taking an interest.  But in the midst of the election blitz, a new report on climate change was released and summarily lost in the hubbub of ballots and campaign ads.  The Intergovernmental Panel on Climate Change (IPCC) published the final draft of its Fifth Assessment Report (AR5) Synthesis Report on November 1st, and although its conclusions won’t surprise anyone knowledgeable about climate change, it’s worthwhile to review the highlights pertaining to the ocean.

The Synthesis Report is divided into four sections.  To paraphrase, they include: Observed Changes, Future Changes, Factors Influencing Adaptation & Mitigation, and Strategies for Adaptation & Mitigation.  Any student interested in climate change could probably predict the content of the first two sections, as they cover the familiar territory of increased greenhouse gas emissions and their impact on parameters such as temperature, sea level, and human health.  Although the risks are familiar, the language used to describe them is strikingly more urgent than in previous IPCC Assessment Reports.  The IPCC is not an alarmist group: their First Assessment Report, published in 1990, concluded that, “[a]lthough the magnitude of the observed warming is broadly consistent with the predictions of climate models, it is of similar magnitude to natural climate variability.”  This cautious diction may have been the product of smaller data sets and less sophisticated climate models, because the IPCC’s language became bolder with subsequent reports.  The Third Assessment Report (2001) posited that “[t]here is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities,” and the most recent AR5 states that “[h]uman influence on the climate system is clear.”  Dwindling uncertainty is also apparent in the phrasing used to describe each threat, with plenty of “virtually certain”s and “high confidence”s peppering the report.  (See the beginning of the document for definitions of the statistical probabilities.)

The oceans (light and dark blue) account for 90% of the energy stored on Earth. Figure from IPCC AR5 Synthesis Report (subject to copy editing).

So what does AR5 have to say about climate change and the ocean?  Well, the ocean surface is certainly warming, on the order of 0.11 ºC per decade from 1971 to 2010, because the oceans stored about 90% of the energy accumulated on the planet during that time.  (The atmosphere, by comparison, stored about 1%.)  Unsurprisingly, sea level increased 0.19 m between 1901 and 2010, but that rise was not evenly distributed.  Over the past ten years, the rate of sea level rise in the West Pacific was up to three times the global average; the East Pacific averaged no change or even a decrease in sea level.  Ocean acidification continues apace, with a pH decrease of 0.1 since the Industrial Revolution, translating to a 26% increase in acidity.  The impact of these changes on marine life includes coral bleaching, thinning of CaCO3 shells, and movement of fish, invertebrates, and phytoplankton to deep, cool waters, usually near the poles.

To forecast future Earth, AR5 models four Representative Concentration Pathways (RCPs) that consider a range of ways humans might respond to climate change, from drastically reducing our greenhouse gas emissions to chugging ahead with business as usual.  The bad news is that all scenarios expect that, by 2100, the planet will likely warm by at least 1.5 ºC, and the ocean will likewise warm throughout the century.  The rate of sea level rise is expected to accelerate, topping the current 2.0 mm/year, and is “virtually certain” to continue “for many centuries beyond 2100.”  The oceans will also continue acidify as they take up CO2.  Climate change alone would impact marine life, but when combined with other anthropogenic stressors such as pollution and overharvesting, the IPCC predicts that “a large fraction of terrestrial, freshwater and marine species face increased extinction risk … during and beyond the 21st century.”  The report specifically notes that this will imperil fisheries at low latitudes.

This map illustrates changes in maximum catch potential for exploited fisheries by midcentury compared with the first decade of the 2000s. The red areas indicate that catch will decrease most substantially at the equator and near Antarctica.  The model only accounts for global warming, and does not include the impacts of overharvesting or ocean acidification. Image from IPCC AR5 Synthesis Report (subject to copy editing).

It’s bleak, no?  And the IPCC’s depressing litany doesn’t stop with the environment.  The Synthesis Report emphasizes that the cumulative impacts of climate change will be most injurious to those already at a disadvantage, such as the poor and those living in conflict zones.  Personally, this is what galls me most about the United States’ response to climate change.  We will certainly have challenges in a warmer future, but although we have contributed substantially to the problem, people in less developed nations will suffer far more than us.  If we were facing famine, inundation, or increased disease, would our response be to smilingly advocate more CFLs or carpooling?  Unilateral action is great; everyone, myself included, wants to feel as though they’re contributing to a solution.  But, as the second two sections of the AR5 Synthesis Report emphasize, adaptation and mitigation need to be embraced by industry and nations to be effectual.  The report suggests that strategies such as reforestation, cleaner energy, and behavioral changes could limit global warming, and it notes that there’s been encouraging work between and within nations on these goals since AR4.

Amidst the onslaught of campaigning leading up to Tuesday’s election, however, I didn’t hear a single comment about the environment beyond damning North Carolina’s Dan River coal ash spill earlier this year.  There are obviously a number of concerning issues facing today’s voter, but shouldn’t the environment at least merit consideration?  What does it say about this country’s priorities that climate change doesn’t even register on voters’ radar and the IPCC’s Synthesis Report just ekes its way onto the Google Science headlines?  The average citizen may think about climate change in strictly environmental terms, and maybe ecological turmoil just doesn’t concern him.  I’m guessing, though, that nearly everyone is troubled by human suffering.  Perhaps the takeaway message from AR5 should be that nations can elect to mitigate climate change, but if they don’t, there will be a lot more suffering to go around.

To view the IPCC’s AR5 Synthesis Report, go to http://ipcc.ch/ and click on “Synthesis Report” in the middle of the page.  The “Summary for Policymakers” and “Headline Statements” provide condensed versions of the Synthesis Report.

Cover image from http://mainlinepatoday.com/2009/10/15/blog-action-day-2009-global-climate-change-think-small/.