Tuesday, December 18, 2012

It's All About Chemistry

In 1827 the French mathematician and scientist, Jean-Baptiste Joseph Fourier postulated that something in the atmosphere was helping keep the earth warmer than it might otherwise.  He is generally credited with discovering the greenhouse effect even though he did not coin the phrase.  However, his work set the stage for later developments in the nineteenth century.

It was the British scientist John Tyndall who demonstrated the absorption of infrared radiation from different gases in 1861.  His work found that nearly all of the greenhouse effect was due to just a few trace gases like water vapor and carbon dioxide (CO2).  This was a startling discovery, because it had huge implications for Earth’s climate.

The Swedish chemist Svante Arrhenius was the first to actually detail how a doubling of carbon dioxide would change the global temperature with the publication of his work in 1896.  His work eventually led to the Nobel Prize in Chemistry in 1903.  He is recognized with beginning modern climate science.

The discovery of global warming is a fascinating story.  I highly recommend the book by Spencer Weart by the name The Discovery of Global Warming.  If you are interested in the scientific papers, it is available in the collection called the The Warming Papers edited by David Archer and Raymond Pierrehumbert.

Note that the foundation of climate science occurred over a century ago.  It is also noteworthy that the trace gases were recognized for their ability to influence Earth’s climate as far back as the nineteenth century.

Fast forward to today.  The burning of fossil fuels has fueled (pardon the pun) the world economic growth.  China and the U.S. are the two largest emitters of CO2.  In the latest accounting the global growth in emissions continues.

How do we know that the increases in CO2 come from burning fossil fuels?

It turns out that burning fossil fuels releases various isotopes of carbon dioxide.  The isotopic ratios are different for living organisms than for long buried fossil fuels.  About 1 in 4 carbon dioxide molecules in the atmosphere come from burning fossil fuels and that is changing rapidly.  A ratio of 1 in 2 carbon dioxide molecules is expected by mid-century.

CO2 molecules in the atmosphere.  A ratio of one in four come from burning fossil fuels.  Image Credit: Climate Central.

Human-generated emissions of carbon dioxide (CO2) this year are expected to reach 35.6 billion tons. That’s up 2.6 percent from what was emitted in 2011, the previous record holder.  This estimate, published recently in Nature Climate Change, is based on economic factors, such as changes to the global GDP, and technological factors, such as improvements in emissions intensity, which predict how many fossil fuels we’re burning, and how efficiently we’re doing it.

Click on the image to enlarge.  Image Credit: Climate Central.

The publication coincided with a report from the World Meteorological Organization (WMO) last week, which officially announced that atmospheric concentrations of CO2 reached a record 390.9 parts per million (ppm) in 2011. That concentration is 40 percent greater than what is was in 1750, before humans started burning fossil fuels in earnest. The concentrations of other greenhouse gases, such as methane and nitrous oxide, also reached record amounts. According to the Global Carbon Project, levels of atmospheric CO2 haven’t been this high since at least 800,000 years ago. Thanks to this, we’re now trapping about 30 percent more solar heat every year than we were 250 years ago.

Thirty-five billion tons a year of CO2 is about 58 percent more than what the world emitted in 1990 – the year the United Nations uses as a baseline for its discussions of how to reduce global emissions. During the 2009 U.N. climate negotiations, countries agreed to keep temperatures from rising more than 2°C (3.6°F) by 2100. However, as emissions have continued to rise, many scientists worry that 2°C of warming by the end of this century may be inevitable.

Projections from the IPCC and the World Bank argue that we could see as much as 4°C (7.2°F) by 2100. According to those projections, we are “virtually certain” to exceed the 2°C target with the current level of cuts pledged by various countries, and have a 50 percent chance of reaching 3°C (4.2°F).

I might add that these estimates are conservative.  Studies from MIT suggest that the warming could be 5°C (9°F) by the end of the century if no action is taken.  This is the mid-point value with an even chance it could be higher.

However, we do not have to wait for the climate to respond.  It already is.  It is speculative to say exactly what the changes will be, but it is safe to say it won’t be pretty.

The bottom line is that the burning of fossil fuels is changing the chemistry of the atmosphere and ocean.  It is resulting in a global warming in both.  Furthermore, in the ocean it is leading to greater acidification which is endangering marine ecosystems.  You do not have to wait.  It is happening now and being observed by scientists worldwide.