Name: _______________________________
Science 1
Carbon Dioxide and Temperature
The following information is from 350.org, an organization started by Bill McKibben, an environmental
scientist from Middlebury College, VT.
350 parts per million is what many scientists, climate experts, and national governments are now saying
is the safe upper limit for CO2 in our atmosphere.
Accelerating arctic warming and other early climate impacts have led scientists to conclude that we are already
above the safe zone at our current 390ppm, and that unless we are able to rapidly return to below 350 ppm this
century, we risk reaching tipping points and irreversible impacts such as the melting of the Greenland ice sheet
and major methane releases from increased permafrost melt.
There are three numbers you need to really understand global warming, 275, 392, and 350.
Since the beginning of human civilization up until about 200 years ago, our atmosphere contained about 275
parts per million of carbon dioxide. Parts per million is simply a way of measuring the concentration of
different gases, and means the ratio of the number of carbon dioxide molecules to all of the molecules in the
atmosphere. 275 ppm CO2 is a useful amount—without some CO2 and other greenhouse gases that trap heat in
our atmosphere, our planet would be too cold for humans to inhabit.
So we need some carbon in the atmosphere, but the question is how much?
Many of the activities we do every day like turning the lights on, cooking food, or heating our homes rely on
fossil fuel energy sources that emit carbon CO2 and other heat-trapping gases into the atmosphere. We're taking
millions of years worth of carbon, stored beneath the earth as fossil fuels, and releasing it into the atmosphere.
By now—and this is the second number—the planet has about 392 parts per million CO2 – and this
number is rising by about 2 parts per million every year.
Scientists are now saying that's too much – that number is higher than any time seen in
the recorded history of our planet—and we're already beginning to see disastrous
impacts on people and places all over the world. Glaciers everywhere are melting and
disappearing fast—and they are a source of drinking water for hundreds of millions of
people. Mosquitoes, who like a warmer world, are spreading into lots of new places, and
bringing malaria and dengue fever with them. Drought is becoming much more
common, making food harder to grow in many places. Sea levels have begun to rise, and
scientists warn that they could go up as much as several meters this century. If that
happens, many of the world's cities, island nations, and farmland will be underwater.
The oceans are growing more acidic because of the CO2 they are absorbing, which
makes it harder for animals like corals and clams to build and maintain their shells and skeletons. Coral reefs
could start dissolving at an atmospheric CO2 concentration of 450-500 ppm. Along with increased intensity of
extreme weather, such as hurricanes and blizzards, these impacts are combining to exacerbate conflicts and
security issues in already resource-strapped regions.
"If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on
Earth is adapted, CO2 will need to be reduced from its current 392 ppm to at most 350 ppm."
That will be a hard task, but not impossible. We need to stop taking carbon out of the ground and putting it into
the air. Above all, that means we need to stop burning so much coal—and start using solar and wind energy and
other such sources of renewable energy. If we do, then the earth’s soils and forests will slowly cycle some of
that extra carbon out of the atmosphere, and eventually CO2 concentrations will return to a safe level. By
decreasing use of fossil fuels, and improving agricultural and forestry practices around the world, scientists
believe we could get back below 350 by mid-century. But the longer we remain in the danger zone—above
350—the more likely that we will see disastrous and irreversible climate impacts.
Sources:

A Safe Operating Space for Humanity. Nature 461, 472-475 (24 September 2009); doi:10.1038/461472a; Published online 23 September 2009

Hansen, James, et al. Target Atmospheric CO2: Where Should Humanity Aim? Submitted April 7, 2008. NASA climate scientist James Hansen's paper
about the 350ppm target.

Hansen, James, et al. Target Atmospheric CO2: Supporting Material. Submitted April 7, 2008.

The IPCC 4th Assessment Report – link to the latest report by the Nobel-prize winning United Nations Intergovernmental Panel on Climate Change,
supported by the world's leading climatologists.

Baer, Paul, Tom Athanasiou and Sivan Kartha. "The Right to Develop in a Climate Constrained World: The Greenhouse Development Rights
Framework" - an important policy framework for how to mitigate climate change while ensuring an equitable path to development for the Global South.

The United Nations Framework Convention on Climate Change - link to the official UNFCCC website with information about the UN climate policy
process.

NASA - scientific reports, interactive maps, resources for kids, and more

RealClimate.org - a blog of climate science, written by climate scientists
Name: _______________________________
Science 1
Carbon Dioxide and Temperature
Read the attached article about carbon dioxide and temperature and then answer the following questions:
1. According to the graph (labeled Figure 1) what is the relationship between carbon dioxide and
temperature? Temperature is the bottom line and carbon dioxide is the top line.
2. Scientists measure the amount of carbon dioxide in the atmosphere in ppm (parts per million). What do
the following carbon dioxide levels represent?
a. 275 ppm:
b. 392 ppm:
c. 350 ppm:
3.
How are humans causing more carbon to be released into the atmosphere?
4.
How are each of the following changing because of excess CO2 in the atmosphere?
a. Glaciers:
b. Mosquitoes:
c. Drought:
d. Sea Levels:
e. Coral reefs:
f. Weather:
5.
How can we get back to 350ppm of CO2?