Temperatures
Earth is getting warmer by virtually every measure we know. The temperature has been well above normal for more than 25 years.
Although increases of 0.6-0.9°C over the last century or so may not sound very threatening, remember that’s a global average, so some places warmed more. Think of a time when you had a fever. Even 1°C made a big difference to how well you felt. In the same way, our planet is becoming feverish.
In South and Central America, studies all show patterns of changes in extremes consistent with general warming, especially more warm nights and fewer cold ones. In the past few decades, temperatures rose most in the Northern Latitudes, but they have also risen in the Southern Hemisphere. Average temperatures increased 0.5°C in Brazil and approximately 1°C in Central and South America.
Annual global mean observed temperatures (1979-2005).
All of Brazil has experienced warming at both the surface and in the upper atmosphere (troposphere).
Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. FAQ 3.1, Figure 1, Cambridge University Press
The Amazon itself has warmed about 0.25°C per decade, a relatively fast rate compared to previous climate changes. When the planet came out of its last ice age about 9,700 BC, the Amazon warmed much more slowly—only about 0.1°C per century.
What do you think?
Looking at the graph, what can you conclude about the global temperatures in 1997? (Choose all that apply.)
The correct answers are b) and e).
Part of the reason 1997 was such a warm year is that a strong El Niño pattern occurred, so the temperatures reflect both natural warming from that phenomenon as well as warming from greenhouse gases. El Niños are periodic changes in the winds and ocean currents in the tropical Pacific Ocean that have important consequences for weather around the globe.
Was the devastating Amazonian drought in 2005 also the result of an El Niño? Although global temperatures that year were also high, scientists have concluded that the dry pattern in the Amazon was due to unusually warm temperatures in the tropical North Atlantic, rather than an El Niño.
