Convention on Climate Change (UNFCCC) established in 1992, and to the 1997
Kyoto Protocol. IPCC organized periodic meetings, resulting in successive complete published documents such as the Fourth Assessment Report (AR4 Report) and
the Fifth Assessment Report (AR5 Report).
The climate system includes five interacting components which are the atmosphere, hydrosphere, ice and cryosphere with permafrost, biosphere, and lithosphere. Climate change is associated with modifications in the Earth’s climate
system, resulting in newer climate patterns and long-term averages of climate
variables with time scales from decades to thousands of years. These changes can
derive from internal variability when natural processes linked to the various components of the climate system modify the global energy budget. Examples of these
processes are cyclical ocean patterns such as the El Niño southern oscillation, the
Pacific decadal oscillation, and the Atlantic multi-decadal oscillation. There is also
external forcing on climate change which includes solar output and volcanism.
Climate change usage refers to a change in the state of the climate that can be
statistically assessed, whether due to human activity or because of natural variability. This variability can be identified by changes in the mean and/or fluctuations
of its properties, and that persists for an extended period, typically decades or
longer. It is worth noticing that this usage differs from that in the United Nations
Framework Convention on Climate Change (UNFCCC), where climate change
refers to a change in climate that is attributed directly or indirectly to human activity
altering the composition of the global atmosphere, and that is in addition to natural
sources of climate variability observed over comparable time.
From 1880 to 2019, the global surface average temperature increase was 0.07 °C
per decade, but has accelerated since 1981 to an average of 0.18 °C per decade.
This tendency is depicted in Fig. 8.1. Considering a 2 °C mean global warming
until 2100, compared with pre-industrial conditions, larger increases in temperature
extremes are expected relative to that average threshold, but with considerable
regional variation. Global climate models project that annual minimum temperatures in the Arctic will reach 5.5 °C, while maximum annual temperatures will be at
least 3 °C warmer over much of the Northern Hemisphere, Central America, and
South Africa (Perkins-Kirkpatrick and Gibson 2017).
In recent decades, changes in climate have caused cascading global impacts in
natural and human systems, indicative of the sensitivity of these systems to climate
change. The evidence supporting the importance of anthropogenic factors over
climate change has grown from the AR4 IPCC to the IPPC AR5 Reports. IPCC
conclusions point to the influence of anthropogenic driving on the average global
surface temperature, the melting and retreat of glaciers, Greenland and Arctic ice
surface loss, and an increase in the energy content of oceans across the 0–700 m
layers and a global mean sea-level rise since the 1970s. Global warming over the
twentieth century was widespread and rather uniform. Warming was about 0.4 °C
in the tropics, 0.6 °C at middle latitudes, and an average of 0.5 °C globally over
100 years. In the temperate Northern Hemisphere, the warming was about twice as
much in the cool season compared to the warm season (Hansen et al. 2001).
8.1 Introduction
269
Kyoto Protocol. IPCC organized periodic meetings, resulting in successive complete published documents such as the Fourth Assessment Report (AR4 Report) and
the Fifth Assessment Report (AR5 Report).
The climate system includes five interacting components which are the atmosphere, hydrosphere, ice and cryosphere with permafrost, biosphere, and lithosphere. Climate change is associated with modifications in the Earth’s climate
system, resulting in newer climate patterns and long-term averages of climate
variables with time scales from decades to thousands of years. These changes can
derive from internal variability when natural processes linked to the various components of the climate system modify the global energy budget. Examples of these
processes are cyclical ocean patterns such as the El Niño southern oscillation, the
Pacific decadal oscillation, and the Atlantic multi-decadal oscillation. There is also
external forcing on climate change which includes solar output and volcanism.
Climate change usage refers to a change in the state of the climate that can be
statistically assessed, whether due to human activity or because of natural variability. This variability can be identified by changes in the mean and/or fluctuations
of its properties, and that persists for an extended period, typically decades or
longer. It is worth noticing that this usage differs from that in the United Nations
Framework Convention on Climate Change (UNFCCC), where climate change
refers to a change in climate that is attributed directly or indirectly to human activity
altering the composition of the global atmosphere, and that is in addition to natural
sources of climate variability observed over comparable time.
From 1880 to 2019, the global surface average temperature increase was 0.07 °C
per decade, but has accelerated since 1981 to an average of 0.18 °C per decade.
This tendency is depicted in Fig. 8.1. Considering a 2 °C mean global warming
until 2100, compared with pre-industrial conditions, larger increases in temperature
extremes are expected relative to that average threshold, but with considerable
regional variation. Global climate models project that annual minimum temperatures in the Arctic will reach 5.5 °C, while maximum annual temperatures will be at
least 3 °C warmer over much of the Northern Hemisphere, Central America, and
South Africa (Perkins-Kirkpatrick and Gibson 2017).
In recent decades, changes in climate have caused cascading global impacts in
natural and human systems, indicative of the sensitivity of these systems to climate
change. The evidence supporting the importance of anthropogenic factors over
climate change has grown from the AR4 IPCC to the IPPC AR5 Reports. IPCC
conclusions point to the influence of anthropogenic driving on the average global
surface temperature, the melting and retreat of glaciers, Greenland and Arctic ice
surface loss, and an increase in the energy content of oceans across the 0–700 m
layers and a global mean sea-level rise since the 1970s. Global warming over the
twentieth century was widespread and rather uniform. Warming was about 0.4 °C
in the tropics, 0.6 °C at middle latitudes, and an average of 0.5 °C globally over
100 years. In the temperate Northern Hemisphere, the warming was about twice as
much in the cool season compared to the warm season (Hansen et al. 2001).
8.1 Introduction
269