Table SPM-2. (WGI) Recent trends, assessment of human influence on the trend, and projections for extreme weather events for
which there is an observed late 20th century trend.
| Phenomenon a and direction of trend |
Likelihood that trend occurred in late 20th century (typically post 1960) |
Likelihood of a human contribution to observed trend b |
Likelihood of future
trends based on
projections for 21st
century using SRES
scenarios |
Table notes:
a See Table 3.7 for further details regarding definitions.
b See Table TS-4, Box TS.3.4 and Table 9.4.
c Decreased frequency of cold days and nights (coldest 10%).
d Warming of the most extreme days and nights each year.
e Increased frequency of hot days and nights (hottest 10%).
f Magnitude of anthropogenic contributions not assessed. Attribution for these phenomena based on expert judgement rather
than formal attribution studies.
g Extreme high sea level depends on average sea level and on regional weather systems. It is defined here as the highest 1%
of hourly values of observed sea level at a station for a given reference period.
h Changes in observed extreme high sea level closely follow the changes in average sea level {5.5.2.6}. It is very likely that
anthropogenic activity contributed to a rise in average sea level. {9.5.2}
i In all scenarios, the projected global average sea level at 2100 is higher than in the reference period {10.6}. The effect of
changes in regional weather systems on sea level extremes has not been assessed. |
| Warmer and fewer cold days and nights over most land |
Very likely c |
Likely d |
Virtually certain d |
| Warmer and more frequent hot days and nights over most land areas |
Very likely e |
Likely (nights) d |
Virtually certain d |
| Warm spells / heat waves. Frequency increases over most land areas |
Likely |
More likely than not f |
Very likely |
| Heavy precipitation events. Frequency (or proportion of total rainfall from heavy falls) increases over most areas |
Likely |
More likely than not f |
Very likely |
| Area affected by droughts increases |
Likely in many regions since 1970s |
More likely than not |
Likely |
| Intense tropical cyclone activity increases |
Likely in some regions since 1970 |
More likely than not f |
Likely |
| Increased incidence of extreme high sea level (excludes tsunamis) g |
Likely |
More likely than not f, h |
Likely i |
Source: IPCC Climate Change 2007: The Physical Science Basis, Summary for Policymakers (2007) 
, p9
Related publication:
Other Figures & Tables on this publication:
Figure SPM-1. (WGI) Changes in Greenhouse Gases from Ice-core and Modern Data
Figure SPM-2. (WGI) Radiative Forcing Components
Figure SPM-3. (WGI) Changes in Temperatures, Sea Level and Snow Cover between 1850 and 2010
Figure SPM-4. (WGI) Global and Continental Temperature Change
Figure SPM-5. (WGI) Multi-model Averages and Assessed Ranges for Surface Warming
Figure SPM-6. (WGI) AOGCM Projections of Surface Temperatures
Figure SPM-7. (WGI) Projected Patterns of Precipitation Changes
Figure SPM-1. (WGII) Changes in physical and biological systems and surface temperature 1970-2004
Figure SPM-2. (WGII) Key impacts as a function of increasing global average temperature change
Figure SPM-1. (WGIII) Emissions of different greenhouse gases 1970-2004
Figure SPM-2. (WGIII) Relative global development of indicators of income, energy supply, CO2 emissions and population for 1970 to 2004
Figure SPM-3a. (WGIII) Distribution of regional per capita greenhouse gas emissions
Figure SPM-3b. (WGIII) Distribution of regional greenhouse gas emissions per unit of income
Figure SPM-4. (WGIII) Global greenhouse gas emissions for 2000, 2030 and 2100
Figure SPM-5a/5b. (WGIII) Estimated global economic mitigation potential
Figure SPM-6. (WGIII) Estimated economic mitigation potential in 2030 as a function of carbon price
Figure SPM-7. (WGIII) Emissions pathways of mitigation scenarios for alternative categories of stabilization levels
Figure SPM-8. (WGIII) Relationship between stabilization scenario categories and equilibrium global mean temperature change
Figure SPM-9. (WGIII) Cumulative emissions reductions for alternative mitigation measures for 2000 to 2030 (left-hand panel) and for 2000-2100 (right-hand panel)
Global greenhouse gas emissions 1970-2004
Table SPM-1. (WGI) Observed rate of sea level rise and estimated contributions from different sources.
Table SPM-2. (WGI) Recent trends, assessment of human influence on the trend, and projections for extreme weather events for
which there is an observed late 20th century trend.
Table SPM-3. (WGI) Projected globally averaged surface warming and sea level rise at the end of the 21st century.
Table SPM-1. (WGII) Examples of possible impacts of climate change due to changes in extreme weather and climate events
based on projections to the
mid- to late 21st century. These do not take into account any changes or developments in adaptive capacity. Examples of all entries are to be found
in chapters in the full Assessment (see source at top of columns). The first two columns of the table (shaded yellow) are taken directly from the
Working Group I Fourth Assessment (Table SPM-2). The likelihood estimates in Column 2 relate to the phenomena listed in Column 1.
Table SPM-4. (WGIII) Estimated global macro-economic costs in 2030a for least-cost trajectories towards different long-term stabilization levels.b,c
Table SPM-5. (WGIII) Characteristics of post-TAR stabilization scenarios
[Table TS 2, 3.10]a
Table SPM-6. (WGIII) Estimated global macro-economic costs in 2050 relative to the baseline for
least-cost trajectories towards different long-term stabilization targetsa
[3.3, 13.3]
Table SPM-7. (WGIII) Selected sectoral policies, measures and instruments that have shown to be
environmentally effective in the respective sector in at least a number of national cases.
Table SPM-1. (WGIII) Global economic mitigation potential in 2030 estimated from bottom-up studies.
Table SPM-2. (WGIII) Global economic mitigation potential in 2030 estimated from top-down studies.
Table SPM-3. (WGIII)
Key mitigation technologies and practices by sector. Sectors and technologies are listed in no particular order. Non-technological practices, such as lifestyle changes, which are cross-cutting, are not included in this table (but are addressed in paragraph 7 in this SPM).
Figure SPM-2. (WGII) Key impacts as a function of increasing global average temperature change
Figure SPM-6. (WGIII) Estimated economic mitigation potential in 2030 as a function of carbon price
Likelihood
The Emission Scenarios of the IPCC Special Report on Emission Scenarios (SRES)
Box SPM-2 (WGIII) Mitigation potential and analytical approaches
Box SPM-3 (WGIII) Assumptions in studies on mitigation portfolios and macro-economic costs
Box SPM-4 (WGIII) Modelling induced technological change
Parties & Observers of the UNFCCC
