Global Climate Change Climate change can be understood by approaching three areas of study:
•
evidence of current and past global climate change
•
drivers of global climate change
•
documented results of climate change
When reading news articles about global climate change, it is useful to keep these three distinct
aspects of climate change clearly distinct. It's important to note that data indicating that the Earth's
climate is changing and the factors causing this climate change are frequently confused in reports and
discussions about global climate change.
Evidence for Global Climate Change Since average temperature and precipitation cannot be directly measured in the past, scientists
must instead measure temperature inferentially. To do this, scientists rely on
historical evidence of Earth’s past climate. A significant piece of this evidence for climate change comes from Antarctic ice cores. These ice
cores are samples of
polar ice that have been extracted using drills that can penetrate ice sheets or
high mountain glaciers thousands of meters. Viewing the ice cores is like going back in time; the
older the time period, the deeper the sample. Air bubbles and other biological remnants trapped within
the ice can provide information about temperature and carbon dioxide levels. Using Antarctic ice
cores, researchers have been able to infer the Earth's temperature over the previous 400,000 years
(Figure 166a). These analyses are an example, and the data in Figure 167 serves as evidence. The 0
°C on this graph refers to the long-term average. Temperatures that are greater than 0 °C exceed
Earth’s long-term average temperature. Conversely, temperatures that are less than 0 °C are less than
Earth’s average temperature. This graph demonstrates that there have been regular cycles of rising
and falling temperatures.
