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Ireland’s Environment – An Assessment 2016
40
Climate change is primarily associated with the increase
in the global average temperature. The average global
temperature in 2015 was 1ºC higher than the pre-
industrial levels. This record level follows three decades
that were successively warmer than any preceding decade
since 1850. However, about 90% of the additional energy
trapped by greenhouse gases (GHGs) is being absorbed
by the oceans. This is contributing to sea-level rise due to
thermal expansion (Figure 3.2). On average, global sea
level has risen by about 20 cm in the last century. Changes
evident in Ireland have tended to follow the global
average, with an average temperature increase of just
under 1ºC over the last century. Since 1993, average sea
level has risen around Ireland by just over 3 cm per decade.
The Responses to Climate
Change
We Know What to Do to Address
Climate Change
There are two linked responses to climate change:
n
mitigation of emissions of the GHGs that are driving
climate change
n
adaptation to reduce vulnerability to the adverse
impacts of climate change.
Mitigation of GHG emissions is the primary response to
the threat of climate change and each country will need to
play its part in taking effective actions. The aim of holding
the increase in the global average temperature to well
below 2°C, relative to pre-industrial temperature, frames
mitigation actions from global to local levels – see topic
box on Paris agreement. To achieve this objective, global
emissions of carbon dioxide and other GHGs must be
brought to near or below zero by the end of this century.
Emissions of carbon dioxide must be reduced to net-zero
before this time. Ireland’s emissions have to follow a
similar trajectory on a shorter timeline (see National Policy
Statement, DECLG,
1
2014).
Failure to take effective action is projected to result in
dangerous and unmanageable global impacts, including
undermining of global food production and major loss of
natural ecosystems, and could cause irreversible flooding
of low-lying coastal areas and loss of small island states.
Projected impacts include major losses of coastal cities,
population movement and likely conflicts over resources.
Adaptation is increasingly recognised as an important
response to climate change, with an adaptation goal
being included in the Paris Agreement (see Box). The aim
1 Note: The Climate Change functions in the former Department of
Environment, Community and Local Government were transferred in
July 2016 to the new Government department, the Department of
Communications, Climate Action and Environment.
Figure 3.1
Schematic of Atmospheric Factors that Determine the Global Energy Balance
(Source: Kiehl and Trenberth, 1997)
Reflected Solar
Radiation
107 Wm
-2
107
342
235
165 30
40
40
350
78
24
67
Reflected by Clouds,
Aerosol and
Atmospheric
Gases
77
Reflected by
Surface
30
Incoming
Solar
Radiation
342 Wm
-2
Outgoing
Longwave
Radiation
235 Wm
-2
Emitted by
Atmosphere
Absorbed by
Atmosphere
Latent
Heat
324
Back
Radiation
324
Absorbed by Surface
168
Absorbed by
Surface
390
Surface
Radiation
78
Evapo-
transpiration
24
Thermals
Emitted by Clouds
Atmospheric
Window
Greenhouse
Gases