Skip to main content

Currently Skimming:

Q&A
Pages 3-12

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 3...
... Indirect estimates of temperature change from such sources as tree rings and ice cores help to place recent temperature changes in the context of the past. In terms of the average surface temperature of Earth, these indirect estimates show that 1989 to 2019 was very likely the warmest 30-year period in more than 800 years; the most recent decade, 2010-2019, is the warmest decade in the instrumental record so far (since 1850)
From page 4...
... 0 1981−2010 average 0 1981−2010 average For example, additional evidence 0 average March March maximum of a warming trend can be found March maximum -20 September March September maximum in the dramatic decrease in the -20 minimum September maximum -20 minimum September -20 minimum extent of Arctic sea ice at its minimum summer minimum (which occurs -40 -40 in September) , the decrease in -40 -40 1955 1985 1965 1975 1995 2005 2015 June snow cover in the Northern 1955 1985 1965 1975 1995 2005 2015 Year 1955 1985 1965 1975 1995 2005 2015 Data: NSIDC Hemisphere, the increases in the Year 1955 1985 1965 1975 1995 2005 2015 Data: NSIDC Year Data: NSIDC Year Northern Hemisphere June snow cover (1967−2019)
From page 5...
... , and by looking instead at the geographical and seasonal patterns of climate change. The observed patterns of surface warming, temperature changes through the atmosphere, increases in ocean heat content, increases in atmospheric moisture, sea level rise, and increased melting of land and sea ice also match the patterns scientists expect to see due to human activities (see Question 5)
From page 6...
... As a result, a substantial fraction of the CO2 emitted from human activities accumulates in the atmosphere, where some of it will remain not just for decades or centuries, but for thousands of years. Comparison with the CO2 levels measured in air extracted from ice cores indicates that the current concentrations are substantially higher than they have been in at least 800,000 years (see Question 6)
From page 7...
... The data show only 0.4 small periodic amplitude variations 0.2 associated with the Sun's 11-year 0.0 cycle. Source: TSI data from Physikalisch-Meteorologisches -0.2 Observatorium Davos, Switzerland, -0.4 on the new VIRGO scale from 1978 to 1980 1985 1990 1995 2000 2005 2010 2015 mid-2018; temperature data for same 1362.5 time period from the HadCRUT4 Measurement of the sun's energy dataset, UK Met Office, Hadley Total solar irradiance (W m–2)
From page 8...
... 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 40 years is broadly consistent with computer model simulations that include increases in CO2 and decreases in stratospheric ozone, each caused by human activities.
From page 9...
... On ice-age timescales, these gradual orbital variations have led to changes in the extent of ice sheets and in the abundance of CO2 and other greenhouse gases, which in turn have amplified the initial temperature change. Recent estimates of the increase in global average temperature since the end of the last ice age are 4 to 5 °C (7 to 9 °F)
From page 10...
... Greenhouse gases absorb some of the infrared energy that Earth emits in so-called bands of stronger absorption that occur at certain wavelengths. Different gases absorb energy at different wavelengths.
From page 11...
... To make reliable change signal and vice-versa, because climate variations on different space and timescales can interact inferences about human-induced with one another. It is partly for this reason that climate change projections are made using climate climate change, multi-decadal and models (see infobox, p.20)
From page 12...
... A short-term slowdown in the warming of Earth's surface does not invalidate our understanding of long-term changes in global temperature arising from human-induced changes in greenhouse gases. Decades of slow warming as well as decades of accelerated warming occur naturally in the climate system.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.