Sunday, May 19, 2013

Just Another Number?

Numbers have meaning only in context.  A temperature of 98.6 degrees F is normal body temperature, but only in context of the mean.  This is not normal for every person.  The S&P 500 crossing 1600 is meaningless unless it is in context of what the market is doing.  Is it going up or down?  How far has it gone from previous levels?  Only then does the number have meaning.

A milestone was reached recently, Thursday, May 9th, at the Mauna Loa Observatory in Hawaii.  Levels of carbon dioxide reached 400 parts per million (ppm) for the first time in human existence.  Daily measurements are made at the observatory of the gases that lead to atmospheric change.  One of the main gases monitored is carbon dioxide (CO2).  Levels of 400.03 and 400.08 ppm were measured independently by the National Oceanic & Atmospheric Administration (NOAA) and Scripps Oceanographic Institute respectively.

Mauna Loa Observatory in Hawaii.  Click on the image for a larger version.  Image Credit: NOAA/ESRL.
This was a daily mean that was measured for the first time.  Hourly measurements exceeded this number quite a few times since mid-April.  The monthly mean of CO2 will likely peak this month, at a level of about 399 ppm, and then fall until October.  It is likely to pass the 400 ppm in the spring of next year.  The yearly mean will not likely cross this level until 2015 or 2016.

The Keeling Curve showing changes in the CO2 concentration since 1958 at the Mauna Loa Observatory.  Click on the image for a larger version.  Image Credit: Climate Central.

The level of CO2 concentration has increased every year since measurements started in 1958.  At that time the level was 316 ppm and the annual increase was about 0.7 ppm.  However, that has increased to an annual increase of 2.1 ppm.

Jim Butler is Director of Global Monitoring at NOAA’s Earth System Research Laboratory (NOAA/ESRL) in Boulder, Colorado, where he has conducted research on climate forcing and ozone depletion for over 20 years. In his current capacity, Dr. Butler oversees the nation’s continuing measurements of atmospheric constituents that affect the world’s climate, including greenhouse and ozone-depleting gases, aerosols, and surface radiation.  He comments that “atmospheric carbon dioxide (CO2) reaching 400 ppm at Mauna Loa is not in itself a significant event.  It is, however, a noteworthy marker of what is significant  ̶  the accelerating growth and persistence of CO2 in the atmosphere.  CO2 is far and away the dominant greenhouse gas emitted by humans, is responsible in good part for recent climate change, and, once emitted, will remain in the ocean-atmosphere system for thousands of years, warming the planet, changing climate, and driving acidification of the oceans. Atmospheric CO2 has been about 280 ppm through almost all of human civilization, yet, primarily in the past century, humans have driven it up to around 400 ppm mainly by burning fossil fuels.  These emissions continue to accelerate unabatedly.”

“That increase is not a surprise to scientists,” said NOAA senior scientist Pieter Tans, with the Global Monitoring Division of NOAA’s Earth System Research Laboratory in Boulder, Colo. “The evidence is conclusive that the strong growth of global CO2 emissions from the burning of coal, oil, and natural gas is driving the acceleration.” 

Indeed global emissions of CO2 have been increasing as the world’s energy demands increased.  Emissions have increased 56% since 1990.  As the demand for energy increases so does the burning of oil, coal, and natural gas.  This includes emissions from China and India where emissions have soared recently.

Global carbon emissions since 1990.  Click on the image for a larger version.  Image Credit: Climate Central.

Prior to the industrial age CO2 levels had varied from 180 to 280 ppm for over 800,000 years with the higher number occurring during interglacial periods.  Levels of 270 to 280 ppm were the norm since the last ice age.

A look at CO2 concentrations over the past 800,000 years.  Click on the image for a larger version.  Image Credit: Climate Central.

Where do the current readings stand in the paleoclimate record?  The last time that CO2 levels were this high occurred during the Pliocene Era 2.6 to 5.2 million years ago.  Levels peaked at around 425 ppm, a level we are likely to reach in the next 10 to 15 years.  The earth was 3 to 4 degrees C warmer than today and sea level was about 20 to 25 meters (65 to 82 feet) higher.

So why aren’t conditions like that now?  The rate of change has been so swift that the earth is only now adjusting to a new state.  It will take time to reach an equilibrium state and it is not clear that we will reach the numbers above.  However, if we come anywhere near this, it will mean a greatly changed planet.

The problem is that we have not reach an equilibrium state and won’t as long as emissions from the burning of fossil fuels continue.  What does this mean for the planet?  I will explore some of the impacts already being felt in the next post.