Climate Change Evidence & Causes Page: 10 of 36
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Q&A
WHAT DO CHANGES IN THE VERTICAL
STRUCTURE OF ATMOSPHERIC TEMPERATURE
FROM THE SURFACE UP TO THE
STRATOSPHERE TELL US ABOUT THE
CAUSES OF RECENT CLIMATE CHANGE?
The observed warming in the lower atmosphere and cooling in the upper atmosphere
provide us with key insights into the underlying causes of climate change and reveal that
natural factors alone cannot explain the observed changes.
In the early 196os, results from mathematical/physical models of the climate system first showed that
human-induced increases in CO2 would be expected to lead to gradual warming of the lower atmosphere
(the troposphere) and cooling of higher levels of the atmosphere (the stratosphere). In contrast, increases
in the Sun's output would warm both the troposphere and the full vertical extent of the stratosphere. At
that time, there was insufficient observational data to test this prediction, but temperature measurements
from weather balloons and satellites have since confirmed these early forecasts. It is now known that the
observed pattern of tropospheric warming and stratospheric cooling over the past 30 to 40 years is broadly
consistent with computer model simulations that include increases in CO2 and decreases in stratospheric
ozone, each caused by human activities. The observed pattern is not consistent with purely natural changes
in the Sun's energy output, volcanic activity, or natural climate variations such as El Niio and La Niia.
Despite this agreement between the global-scale patterns of modelled and observed atmospheric tem-
perature change, there are still some differences. The most noticeable differences are in the tropical tropo-
sphere, where models currently show more warming than has been observed, and in the Arctic, where the
observed warming of the troposphere is greater than in most models.8 CLIMATE CHANGE
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National Academy of Sciences (U.S.). Climate Change Evidence & Causes, report, Date Unknown; (https://digital.library.unt.edu/ark:/67531/metadc949508/m1/10/: accessed March 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.