The Truth about Global Warming
As seen through the eyes of a physicist
Dr. Suzanne Willis, Ph.D
Northern Illinois University
June 29,2011
Basic physics of warming is well
understood
The greenhouse effect is (mostly) our friend.
Without it the earth would be frozen solid.
The temperature of the outer atmosphere is
around -19C (-2F); without the greenhouse
effect the surface would be the same
temperature.
It is not; it averages about 14C (57F). The
difference comes from greenhouse gases in the
atmosphere.
Composition of the atmosphere
The atmosphere is mostly nitrogen,
oxygen, and argon. However, all of
these are transparent to infrared
radiation and do not contribute to
surface warming.
Most of the warming comes from
carbon dioxide and from water
vapor. Due to their molecular
structure, these molecules absorb
incoming sunlight and reradiate it in
all directions, resulting in warming
of the earth’s surface.
Contributions of water vapor and
carbon dioxide
The pie charts on the previous slide are for the dry
atmosphere. The amount of water vapor in the
atmosphere changes daily but is constant averaged
over time (it comes from open water sources on the
surface), except that the average value rises as the
average temperature rises.
The amount of carbon dioxide fluctuates seasonally
and also over longer periods of time; however in
the past century it has been artificially elevated due
to burning of fossil fuels. This has resulted in a
corresponding increase in temperature.
Carbon dioxide in the atmosphere
This plot shows CO2
emissions and
atmospheric
concentrations since 1751.
This plot shows detailed
measurements of CO2
concentrations in the
atmosphere as a monthly
total and a moving
average.
Carbon dioxide in the atmosphere
Fossil fuels have been deposited over hundreds
of millions of years, and the isotopic
composition of the carbon in them is different
from carbon that comes from living plants.
Isotopic measurements on atmospheric CO2
show that the excess comes from fossil fuels and
not from live plants.
Much of the CO2 that is emitted goes into the
oceans, whose acidity has increased as a result.
Evidence for Global Warming and
Climate Change
Air temperature is increasing over land and sea.
Evidence for Global Warming and
Climate Change
Sea temperature is rising.
Evidence for Global Warming and
Climate Change
Amount of energy stored in the oceans as heat
is rising.
Evidence for Global Warming and
Climate Change
Species are migrating towards the poles and
towards higher elevations.
Ice sheets are melting.
Evidence for Global
Warming and
Climate Change
Glaciers are melting.
Snow cover is
decreasing.
Spring is coming earlier.
Humidity is increasing.
Climate is not weather
Single events, no matter how impressive, cannot
be used as evidence for or against climate
change. It takes the accumulation of many
events over many years.
Heat is a form of energy; as the average
temperature increases we expect to see more
extreme weather, consistent with what has been
observed.
Global warming is not local
In order to understand what is happening to the
planet as a whole, you need to look at global
patterns and events.
Effects of rapid increases in
atmospheric CO2
• More extreme weather
• Tropical diseases and plants moving into
previously temperate climes
• Rising sea levels
• More – see references
The rate of change makes it difficult for adaptation,
either natural or assisted
The most technological societies tend to be the
most vulnerable to disruption
Fossil fuels are running out
At current rates of consumption, assuming the
current rate of increase does not change, oil,
gas, and coal will all be gone in about 40 years
(according to data from GE).
Visualization