Over the period 2081–2100, significant differences in global surface temperatures, relative to the period 1986–2005, are forecasted among the 4 RCP profiles,
with likely increases from 0.3 to 1.7 °C for RCP2.6, 1.1 to 2.6 °C for RCP4.5, 1.4
to 3.1 °C for RCP6.0, and 2.6 to 4.8 °C for RCP8.5.
If a comparison is made with the second half of the nineteenth century, the
forecasted increases in global surface temperatures are higher than 1.5 °C for
RCP4.5 and higher than 2 °C for RCP6.0 and RCP8.5. The average linear global
trending combining land and ocean surface temperature data shows an average
warming of 0.85 °C, over the period 1880–2012. In the Northern Hemisphere, the
warmest 30-year period over the last 1400 years was likely the one found from
1983 to 2012, and each decade between 1984 and 2014 was successively warmer
than any previous decade since 1850. Average Arctic temperatures have increased
at almost twice the global average rate in the past 100 years. Also, the annual mean
of sea ice Arctic extent decreased over the period 1979–2012 at a rate of 3.5–4.1%
per decade.
Global temperatures show multi-decadal average warming, along with variability at smaller annual and decadal scales. Due to this pattern of variability, trends
based on short records are very sensitive to periods selected for evaluations, not
reflecting long-term climate trends generally (AR5 Report).
Predictions from global circulation models, showing a non-uniformity of global
warming in the twenty-first century with changes in the hemisphere, season, and
underlying surfaces, along with seasonal and inter-annual variability, were carried
out by Boer et al. (2000). Land average warming will be higher than over oceans
and, on a global scale, warming will be faster over the Arctic region. At daily and
seasonal scales, frequent hot and fewer cold temperatures over most land areas are
almost certain to occur along with an increase in the mean global temperature. Also,
longer heatwaves, with higher frequency and sporadic winter extremes, will likely
take place.
Ocean warming, especially near the surface, dominates the increase in energy
stored in the climate system, accounting for more than 90% of the energy accumulated over the period 1971–2010, with only about 1% stored in the atmosphere.
Over the same period, the upper 75-m depth of oceans on a global scale warmed at
about 0.11 °C per decade, with the warming of the upper 700 m likely beginning in
the 1870s.
The physical and geographical context for rainfall provides the essential framework for the analysis of patterns and intensity of precipitation (Stull 2000). Basically, the convergence of moisture-laden air masses leads to air uplift, cloud
formation, and delivery of precipitation, snow, or hail. Atmospheric water vapor is
central to this dynamic, insofar as the warm atmosphere can convey water vapor
amounts as high as 6–7% per °C of warming near the Earth’s surface, as expressed
by the Clausius–Clapeyron principle. As water vapor also contributes to radiative
cooling of the atmosphere, this later type of radiative forcing induces an additional
in total global precipitation of only about 2–3%, per ºC of warming. This radiative
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8 Fundamentals of Global Carbon Budgets and Climate Change
with likely increases from 0.3 to 1.7 °C for RCP2.6, 1.1 to 2.6 °C for RCP4.5, 1.4
to 3.1 °C for RCP6.0, and 2.6 to 4.8 °C for RCP8.5.
If a comparison is made with the second half of the nineteenth century, the
forecasted increases in global surface temperatures are higher than 1.5 °C for
RCP4.5 and higher than 2 °C for RCP6.0 and RCP8.5. The average linear global
trending combining land and ocean surface temperature data shows an average
warming of 0.85 °C, over the period 1880–2012. In the Northern Hemisphere, the
warmest 30-year period over the last 1400 years was likely the one found from
1983 to 2012, and each decade between 1984 and 2014 was successively warmer
than any previous decade since 1850. Average Arctic temperatures have increased
at almost twice the global average rate in the past 100 years. Also, the annual mean
of sea ice Arctic extent decreased over the period 1979–2012 at a rate of 3.5–4.1%
per decade.
Global temperatures show multi-decadal average warming, along with variability at smaller annual and decadal scales. Due to this pattern of variability, trends
based on short records are very sensitive to periods selected for evaluations, not
reflecting long-term climate trends generally (AR5 Report).
Predictions from global circulation models, showing a non-uniformity of global
warming in the twenty-first century with changes in the hemisphere, season, and
underlying surfaces, along with seasonal and inter-annual variability, were carried
out by Boer et al. (2000). Land average warming will be higher than over oceans
and, on a global scale, warming will be faster over the Arctic region. At daily and
seasonal scales, frequent hot and fewer cold temperatures over most land areas are
almost certain to occur along with an increase in the mean global temperature. Also,
longer heatwaves, with higher frequency and sporadic winter extremes, will likely
take place.
Ocean warming, especially near the surface, dominates the increase in energy
stored in the climate system, accounting for more than 90% of the energy accumulated over the period 1971–2010, with only about 1% stored in the atmosphere.
Over the same period, the upper 75-m depth of oceans on a global scale warmed at
about 0.11 °C per decade, with the warming of the upper 700 m likely beginning in
the 1870s.
The physical and geographical context for rainfall provides the essential framework for the analysis of patterns and intensity of precipitation (Stull 2000). Basically, the convergence of moisture-laden air masses leads to air uplift, cloud
formation, and delivery of precipitation, snow, or hail. Atmospheric water vapor is
central to this dynamic, insofar as the warm atmosphere can convey water vapor
amounts as high as 6–7% per °C of warming near the Earth’s surface, as expressed
by the Clausius–Clapeyron principle. As water vapor also contributes to radiative
cooling of the atmosphere, this later type of radiative forcing induces an additional
in total global precipitation of only about 2–3%, per ºC of warming. This radiative
280
8 Fundamentals of Global Carbon Budgets and Climate Change