Module 63

Figure 63.1

Shows changes in atmospheric CO2 over time. CO2 levels have risen steadily since measurement began in 1958. This increase over time correlated to increased human emissions of carbon from the combustion of fossil fuels and net destruction of vegetation.

What is the evidence that solar radiation is less important to global warming than the increase in greenhouse gases?

There is a historic correlation of CO2 and temperature

Scientists can estimate global temperatures and greenhouse gas concentrations for over 5,000 years

Using a variety of indirect indicators including air bubbles trapped in ancient ice cores, scientists have found that for more than 400,000 years, CO2 concentrations never exceeded 300 ppm. After 1950, CO2 concentrations have sharply increased to their current level of nearly 400 ppm.

Charles David Keeling

First to overcome the technical difficulties in measuring CO2. He found out that Co2 levels varied seasonally and that the concentration of Co2 increased from year to year.

Which is an example of a negative feedback?

Higher CO2 concentrations cause increased photosynthesis.

CO2 emissions differ among nations

When we consider the total amount of CO2 produced by a country we see that the largest contributors are the developed and rapidly changing countries of the world. On a per capita basis, some major CO2 emitters have relatively low per capita CO2 emissions (China)

Seasonal variation

in the spring there is more photosynthesis happening then in the fall; therefore, there is monthly variation of CO2 since the average CO2 is greater in the spring than in the winter, etc.

Feedbacks can increase or decrease the impact of climate change

(a) Temperature and CO2 represent a positive feedback system. When the concentration of CO2 increases in the atmosphere, it can cause global temperatures to increase. This in turn can cause more rapid decomposition, thereby releasing even more CO2 into the atmosphere. (b) Carbon dioxide and producers represent a negative feedback system. Increased CO2 in the atmosphere from anthropogenic sources can be partially removed by increased photosynthesis by producers.

How much has the average global temperature increased in the last 120 years?

1.4 degrees F

If the annual rate of CO2 increase is 1.5 ppm and the concentration in 2010 is 390 ppm, what concentration would you expect in 2100?

525 ppm

Global temperatures have steadily increased since records began in 1880

Although annual mean temperatures can vary from year to year, temperatures have exhibited a slow increase from 1880 to 2012. This pattern becomes much clearer when scientists compute the average temperature each year for the past 5 years.

Which data are used to estimate historic temperatures and carbon dioxide concentrations? I. Marine organism fossils II. Air trapped in ice III. Glacier depth

I and II only

IPCC

Intergovernmental Panel on Climate Change, panel of scientists and researchers has been one of the main bodies in environmental control and standards in the international community

ocean acidification

The process by which an increase to ocean CO2 causes more CO2 to be converted to carbonic acid, which lowers the pH of the water