According to Mann et al. (1998), the years 1990, 1995, and 1997 were warmer
than any other since 1400 AD, within a 99.7% level of certainty. In the past,
unforced natural climate variability, relevant in century time scales, was due to
natural variations of solar irradiance or explosive volcanism. If a credible empirical
description of climate variability could be obtained these authors noted that for the
last centuries, it would be possible a more confident estimation about the roles of
different external and internal forces of variability on the past and recent climate.
Figure 8.2 depicts the estimates of the increases of CO 2 in the atmosphere (red line)
along with human emissions (blue line) since the start of the Industrial Revolution
in 1750. Emissions rose slowly to about 5 billion tons a year in the mid-twentieth
century before a sharp increase to more than 35 Gty
−1 forescast by the end of the
century (Mitra 2020).
Cumulative emissions of CO 2 and other greenhouse gases will largely determine
global mean surface warming by the late twenty-first century and beyond. There is
also evidence that the negative impacts of climate change on crop yield will
override any positive impacts. Available evidence suggests that in higher latitudes
there could be positive effects, although it is not yet clear if the overall balance is
positive (AR5 Report 2015).
In tropical and temperate regions, the balance of climate change effects is
negative, especially in relation to the cultivation of cereal crops such as wheat, rice,
and maize. Projections of greenhouse gas emissions vary over a wide range,
depending on socioeconomic factors, developmental state, and climate policy.
Improvements in climate models, since the AR4 to AR5 Reports, were evident in
topics such as the simulations of continental-scale surface temperature, large-scale
precipitation, monsoon, Arctic sea ice, ocean heat content, some extreme events, the
Fig. 8.1 Records of average global surface temperature from 1880 to 2019, the period with
reliable information. The zero line is indicative of the long-term global average surface
temperature. The blue and red bars show the average differences above or below for each year
(adapted from NOAA/CLIMATE.GOV)
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8 Fundamentals of Global Carbon Budgets and Climate Change
than any other since 1400 AD, within a 99.7% level of certainty. In the past,
unforced natural climate variability, relevant in century time scales, was due to
natural variations of solar irradiance or explosive volcanism. If a credible empirical
description of climate variability could be obtained these authors noted that for the
last centuries, it would be possible a more confident estimation about the roles of
different external and internal forces of variability on the past and recent climate.
Figure 8.2 depicts the estimates of the increases of CO 2 in the atmosphere (red line)
along with human emissions (blue line) since the start of the Industrial Revolution
in 1750. Emissions rose slowly to about 5 billion tons a year in the mid-twentieth
century before a sharp increase to more than 35 Gty
−1 forescast by the end of the
century (Mitra 2020).
Cumulative emissions of CO 2 and other greenhouse gases will largely determine
global mean surface warming by the late twenty-first century and beyond. There is
also evidence that the negative impacts of climate change on crop yield will
override any positive impacts. Available evidence suggests that in higher latitudes
there could be positive effects, although it is not yet clear if the overall balance is
positive (AR5 Report 2015).
In tropical and temperate regions, the balance of climate change effects is
negative, especially in relation to the cultivation of cereal crops such as wheat, rice,
and maize. Projections of greenhouse gas emissions vary over a wide range,
depending on socioeconomic factors, developmental state, and climate policy.
Improvements in climate models, since the AR4 to AR5 Reports, were evident in
topics such as the simulations of continental-scale surface temperature, large-scale
precipitation, monsoon, Arctic sea ice, ocean heat content, some extreme events, the
Fig. 8.1 Records of average global surface temperature from 1880 to 2019, the period with
reliable information. The zero line is indicative of the long-term global average surface
temperature. The blue and red bars show the average differences above or below for each year
(adapted from NOAA/CLIMATE.GOV)
270
8 Fundamentals of Global Carbon Budgets and Climate Change