Wednesday, January 21, 2015

Crossing the boundaries

In 2009, a paper was published that measured where humanity stood in respects to the safe operating boundaries for nine environmental parameters (Rockström et al. 2009).  The nine they chose were climate change, ocean acidification, stratospheric ozone depletion, rate of biodiversity loss, biogeochemical cycles (specifically, the nitrogen and phosphorus cycles), global freshwater use, change in land use, atmospheric aerosol loading, and chemical pollution.  Using the Holocene as a baseline, they calculated threshold levels for each parameter that, when crossed, created a high risk for changes that would be damaging for human civilization.

Rockström et al. found that humanity had crossed the safe boundaries for three of the seven defined parameters in 2009 (two boundaries had yet to be defined):
  1. Climate change, with both CO2 (then 387 ppmv) and change in radiative forcing (1.5 W/m2) exceeding the respective 350 ppmv and 1 W/m2 boundary levels, 
  2. Biodiversity loss, with then extinction rate of >100 species/million species/year far exceeding the boundary of 10 species/million species/year, and 
  3. Biogeochemical cycles, with the then amount of fixed nitrogen per year (121 million metric tons) far exceeding the boundary of 35 million metric tons.  Meaning we've really screwed up the natural nitrogen cycle to go with the messed up carbon cycle.
Figure 1 from Rockström et al. (2009) showing the nine planetary boundaries as well as those which humanity had exceeded.
An update to Rockström et al. was published in Science on January 15, 2015.  Steffen et al. (2015) provided revised boundaries and rates of change.  Their results are sobering, to say the least, as they showed that we still exceed the boundaries on climate change, biodiversity loss, and biogeochemical cycles.  Indeed, recent research has shown the problems to be growing worse (e.g. McCauley et al. 2015 showed that impacts on biodiversity in the oceans is increasing).

Revised planetary boundaries from Steffen et al. (2015).
The portion of their results that gained the most attention was that land-use changes (called land system change in the new paper) now exceeded the planetary boundary of 15% of land converted to cropland.  This means that humans have now crossed four of the seven quantified boundaries.  Just as significant, in my view, is the fact that the updated numbers show that we've also crossed the boundary for the phosphorus cycle.  In 2009, the rate at which we use phosphorus hadn't exceeded the 11 million metric tons per year boundary.  Now it too joins the list of natural biogeochemical cycles that have been completely altered by human activities.

Why is the phosphorus cycle important?  Phosphorus, like nitrogen, is a key limiting nutrient to plant growth, both in terrestrial and in aquatic habitats.  Excess phosphorus leads to algal and cyanobacteria blooms in freshwater (think of what happened to Toledo, Ohio, last summer when a cyanobacteria bloom contaminated their drinking water) and dead zones in marine habitats.  Dead zones have been detected worldwide, from the Chesapeake Bay and the Gulf of Mexico to the Baltic Sea to southern Australia.  This creates numerous problems for aquatic animals (after all, every animal needs oxygen) as well as humans.

Map showing the locations of known dead zones.  From NASA GES DISC.
While the new work has gained some criticism (and the whole concept of planet-wide boundaries is controversial), I think it provides a useful framework for quantifying just how we as a civilization are progressively degrading our environment.  What should happen is that policymakers begin serious discussions and craft proposals to reverse the damage that has already been done and to keep humanity within the safe limits.  In some countries, that may happen.  In the US, unfortunately, what will happen is political gridlock amid proposals to undo much of the meager progress that has been made (see, for example, the various proposals now in Congress to make it harder for presidents to set aside public lands for monuments and parks), with nothing being done until a crisis hits.  As usual.

Friday, January 16, 2015

2014 among the hottest years on record.

This is an update to my previous post on this topic, which was based largely on January-November data.  The full-year data is rolling out and no matter who is measuring, 2014 was a hot year for the Earth.

Wednesday, January 14, 2015

No, a cold snap in the US does NOT mean that global warming has stopped.

This feels like I'm in the movie Groundhog Day.  If there's a cold snap in the US, there's some science denier citing it as "proof" that there's no global warming.  This argument fails for multiple reasons.

Thursday, January 8, 2015

John L. Casey and climate denial

An anonymous commentator on my post about Tom Luongo raised the issue of John Casey and his views on climate change.  This is a valid challenge, since Luongo apparently got much of his misinformation from Casey.

Monday, January 5, 2015

Where is climate change headed?

With the completion of yet another circle around the sun, it's time to take stock of where we're headed with global climate.  I'm going to do something that is somewhat risky—extend statistical models beyond the data range that was used to create them, but necessary if we want to see where current trends will take us in the future.

Wednesday, December 24, 2014

Extinction is forever

Here's a study I missed when it first came out two weeks ago:

Monastersky, R. 2014. Biodiversity: Life—a status report. Nature 516:159-161.

This report compiled all known data on species status.  The results are sobering.  Thousands of species are at risk of extinction, including:
41% of all known amphibians
26% of all known mammals
13% of all known birds
Note: Those are the species currently at risk.  Today.  Not predicted to be at risk in the future.  Forty-one percent of all amphibians, 26% of all mammals, and 13% of all birds are already at risk of extinction today.  And those are the best known groups. The rest—insects, plants, fungi, fish, etc?  Unknown, as not enough species in those groups have been evaluated to even guess at the percentage currently at risk of extinction.

Saturday, December 20, 2014

The non-existant pause in global temperatures

Regular readers of this blog will know that I am skeptical of claims that global warming in atmospheric temperatures have paused since 1998, having written several posts questioning the existence of such a pause.  In this edition, I'll run down the main evidence that, in my opinion, show that the pause is a figment of the denialsphere's imagination.