Regarding the rise in the global mean sea level, the loss of ice mass from the ice
sheets is the main cause [6]. The loss of Arctic (and sub-Arctic) sea ice is of
particular importance with a long-term decline in all months during the satellite
monitoring period (1979–present), with the largest relative losses in late summer,
September. The Arctic summer minimum daily sea-ice extent (4.15 million km
2 )
observed in 2019 was the second lowest on record. Antarctic sea-ice extent had
shown a small long-term increase until 2016, but in late 2016, a drop in extent to
extremely low values was observed and remaining at relatively low levels since
then. During 2019, May, June and July were months with record-low monthly
extents.
Sea level has been monitored with high-precision altimetry instrumentation since
January 1993, providing accurate estimates of an average rise of 3.24 ± 0.3 mm/y,
with the rate increasing over that time. In this period, the global mean sea level
reached its highest in 2019. Although sea-level rise is not regionally uniform, due to
geographical variations in the ocean heat content [7] and to processes involving the
atmosphere, geosphere and cryosphere, its influence has been tangible in coastal
flood risk areas around the world, particularly when associated with storm surges,
putting human settlements and diverse ecosystems at risk of disappearance.
In the last decade, the ocean absorbed around 23% of annual CO 2 emissions [4]
which helps to mitigate the impact of climate change. However, CO 2 reacts with
seawater which decreases its pH and therefore the acidity of the ocean. Ocean
acidity has increased by approximately 25% (decrease of 0.1pH units) since
pre-industrial times [8], and observations from open-ocean sources show a clear
decrease in average pH in the last 20 to 30 years [4]. This acidification process
interferes with the carbonate chemistry that hampers the ability of some marine
organisms, as crustacean and corals, to calcify. Marine life is suffering from these
effects, with negative effects in the potential for growth and reproduction. The
acidification and ocean warming have transformative impacts on coral reef
ecosystems, being coral recruits more susceptible to bleaching and death during the
warmest months of the year.
The changed climate system has been pushing extreme events for new records,
as is the case of heatwaves. A heatwave occurs when the threshold (e.g. maximum
daily temperature, P90) is exceeded for at least three consecutive days. The
thresholds’ value may vary from one place to another, according to the local
conditions. Several major heatwaves were registered in 2019. Two heatwaves
occurred in Europe in late June and late July were very significant with several
records registered. The first one reached its maximum intensity in southern France
(national record of 46.0 °C), while the second was more extensive, with national
records set in several countries (42.6 °C in Germany, 40.7 °C in the Netherlands,
41.8 °C in Belgium, 40.8 °C in Luxembourg, 38.7 °C in United Kingdom and 33.2
°C in Finland) [4]. These temperature records pose a substantial risk to human
health, particularly to elderly, fuel devastating wildfires in vast areas of Siberia,
trigger the Greenland ice sheet melting at a near record rate, and increased the risk
of drought across wide areas of central and eastern Europe.
Carbon Economy and Carbon Footprint
7
sheets is the main cause [6]. The loss of Arctic (and sub-Arctic) sea ice is of
particular importance with a long-term decline in all months during the satellite
monitoring period (1979–present), with the largest relative losses in late summer,
September. The Arctic summer minimum daily sea-ice extent (4.15 million km
2 )
observed in 2019 was the second lowest on record. Antarctic sea-ice extent had
shown a small long-term increase until 2016, but in late 2016, a drop in extent to
extremely low values was observed and remaining at relatively low levels since
then. During 2019, May, June and July were months with record-low monthly
extents.
Sea level has been monitored with high-precision altimetry instrumentation since
January 1993, providing accurate estimates of an average rise of 3.24 ± 0.3 mm/y,
with the rate increasing over that time. In this period, the global mean sea level
reached its highest in 2019. Although sea-level rise is not regionally uniform, due to
geographical variations in the ocean heat content [7] and to processes involving the
atmosphere, geosphere and cryosphere, its influence has been tangible in coastal
flood risk areas around the world, particularly when associated with storm surges,
putting human settlements and diverse ecosystems at risk of disappearance.
In the last decade, the ocean absorbed around 23% of annual CO 2 emissions [4]
which helps to mitigate the impact of climate change. However, CO 2 reacts with
seawater which decreases its pH and therefore the acidity of the ocean. Ocean
acidity has increased by approximately 25% (decrease of 0.1pH units) since
pre-industrial times [8], and observations from open-ocean sources show a clear
decrease in average pH in the last 20 to 30 years [4]. This acidification process
interferes with the carbonate chemistry that hampers the ability of some marine
organisms, as crustacean and corals, to calcify. Marine life is suffering from these
effects, with negative effects in the potential for growth and reproduction. The
acidification and ocean warming have transformative impacts on coral reef
ecosystems, being coral recruits more susceptible to bleaching and death during the
warmest months of the year.
The changed climate system has been pushing extreme events for new records,
as is the case of heatwaves. A heatwave occurs when the threshold (e.g. maximum
daily temperature, P90) is exceeded for at least three consecutive days. The
thresholds’ value may vary from one place to another, according to the local
conditions. Several major heatwaves were registered in 2019. Two heatwaves
occurred in Europe in late June and late July were very significant with several
records registered. The first one reached its maximum intensity in southern France
(national record of 46.0 °C), while the second was more extensive, with national
records set in several countries (42.6 °C in Germany, 40.7 °C in the Netherlands,
41.8 °C in Belgium, 40.8 °C in Luxembourg, 38.7 °C in United Kingdom and 33.2
°C in Finland) [4]. These temperature records pose a substantial risk to human
health, particularly to elderly, fuel devastating wildfires in vast areas of Siberia,
trigger the Greenland ice sheet melting at a near record rate, and increased the risk
of drought across wide areas of central and eastern Europe.
Carbon Economy and Carbon Footprint
7