Environmental Engineering Reference
In-Depth Information
emissions (from burning oil, natural gas and coal) represent just over
eighty percent of the country's man-made greenhouse gas emissions. In
New Zealand the energy sector only contributes about 43 percent of total
emissions: there, agriculture accounts for 48 percent of the country's total.
Indeed, the largest single source of New Zealand's emissions takes the
form of methane from the stomach belches of the country's large popula-
tion of ruminant animals, predominantly sheep. Since these animals have
been bred by New Zealand's livestock industry, these emissions count as
man-made or, as the Greek-origin word has it, anthropogenic.
The IPCC and the Fourth Assessment Report
The Intergovernmental Panel on Climate Change is the scientific body,
created under the United Nations Framework Convention on Climate
Change, that monitors global warming. It collates and assesses informa-
tion from a global network of experts, and is the most important infor-
mation source in determining global policy on climate change. The IPCC
published its Fourth Assessment Report in 2007 and its findings were
alarming, to say the least. “The global atmospheric concentration of car-
bon dioxide has increased from a pre-industrial value of about 280ppm
to 379ppm in 2005. The atmospheric concentration of carbon dioxide
in 2005 exceeds by far the natural range over the last 650,000 years (180
to 300ppm) as determined from ice cores. The annual carbon dioxide
concentration growth rate was larger during the last 10 years (1995-2005
average: 1.9ppm per year) than it has been since the beginning of con-
tinuous direct atmospheric measurements (1960-2005 average: 1.4ppm
The Kaya Identity
This is not the title of a thriller, but an equation written by a Japanese econo-
mist, Yiochi Kaya. It neatly summarizes the factors driving the world's man-
made carbon dioxide emissions. Here it is:
CO
2
= Output (population x GDP) x Energy Intensity (energy use/GDP) x
Carbon Intensity (CO
2
/energy use)
What it highlights is the difficulty in slowing emissions. They will go on rising
because of population growth and income growth - two things no politician
would dare to campaign against - unless, that is, there is an offsetting reduc-
tion in energy intensity and/or in carbon intensity. Our best hope for reducing
energy intensity lies in radically increasing our energy efficiency, while the best
chance of reducing carbon intensity lies in new technology. Both of these aims
require a subtantial amount of political will and international cooperation.
