Page 333 - Earth's Climate Past and Future
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CHAPTER 17
Climatic Changes
Since the 1800s
The climatic proxies summarized in Chapter 16 show that the rate and
amount of warming since 1900 has been unprecedented compared to changes
during the previous 1000 years. This chapter examines this recent (and current)
warming in greater detail. Prior to the middle 1900s, most climatic records
were made with instrumental measurements at Earth’s surface, including
thermometer measurements on land and at sea and field studies of glacier
length. Changes in sea level can also be reconstructed from tide gauges after
correction for the lingering effects of the last deglaciation. Over the last few
decades, satellite measurements of the extent of sea ice and snow cover, of
growing-season length, and of ice sheet mass balance have also become avail-
able. All these measurements show that climate warmed significantly during
the last century and the early parts of this one. The measurements also reveal
shorter-term (multiannual to decadal) oscillations in climate across smaller
regions of the globe.
