1. Update on the 5th Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC)

© Yann Arthus-Bertrand / Altitude

Working Group I Contribution to the IPCC Fifth Assessment

Report Climate Change 2013:

The Physical Science Basis:

SPM

Source: Jose A. Marengo

RE, Chapter 2 WGI

Presented by:

ROSALINA G. DE GUZMAN

Chief, Climate Data Section


Outline of Presentation

• Observed Changes in the Climate • What’s Causing these Changes? • Future Projections of Climate Change • Main Conclusions and Key Uncertainties


What is the IPCC? • Intergovernmental Panel on Climate Change

• Sponsored by: – United Nations Environmental Programme (UNEP)

– World Meteorological Organization (WM))

• Chartered to “Assess” the state of scientific knowledge of Climate Change and produce periodic (every 5 years) a report of their findings.

• 5th Assessment was released September 2013(4Th was on 2007)


Part 1: Observed changes to

the climate



Atmospheric CO2 levels are unprecedented for

800,000 yrs

Atmospheric CO2 concentrations have

– increased by about 40% since 1750, due to human activity

– exceed values recorded in ice cores for the last 800,000 years


Most global land areas analysed have experienced significant warming including of

both maximum and minimum temperature extremes since 1950.


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2000s: warmest decade on record

• Last 3 decades warmest

in instrumental record.

• From palaeoclimate

records, in the NH, last

30 years likely (66-100%)

the warmest period of the

past 1400 years.

• Very likely (90-100%) that number of warm days has increased and cold nights decreased globally


•Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the

energy accumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0−700 m)

warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971.

10


Annual mean Arctic summer sea ice

start of satellite

data

Annual mean Arctic summer sea ice extent decreased

very likely with a rate of 3.5-4.1% per decade in 1979 – 2012

decrease was most rapid in summer (high confidence).

Data normalized to the satellite measured sea ice extent in 1979

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Part 2: What are the causes of

the changing climate?


Radiative Forcing

• Definition: A change in the net radiation at the top of the

atmosphere due to some external factor.

Net radiation = Incoming - Outgoing

Positive net radiation

Incoming > Outgoing

Negative net radiation

Outgoing > Incoming

Positive forcing warming

Negative forcing cooling


Changes to Earth’s Energy Budget

The AR5 estimate for 2011 is 44% greater than the AR4 estimate for 2005 because of:

– Increased forcing from greenhouse gases

– Revised estimate of aerosol forcing


Attribution of Radiative Forcing to Emissions






Part 3: Future projections


Scenarios for future change

• AR4: Special Report on Emission

Scenarios (SRES) are four major

families of GHG emission scenarios

each making different assumptions

for future greenhouse gas pollution,

land-use and other driving forces

• AR5: Representative Concentration

Pathways (RCPs) are four GHG

concentration trajectories, each

describing a different future value of

radiative forcing in 2100. RCPs aim to

provide a range of climate model

responses, rather than being derived

from socio-economic storylines.


What is RCP? • Representative Concentration Pathways (RCPs) are four greenhouse gas concentration (not

emissions) trajectories adopted by the IPCC for its fifth Assessment Report (AR5).[1]

• The pathways are used for climate modeling and research. They describe four possible climate

futures, all of which are considered possible depending on how much greenhouse gases are

emitted in the years to come. The four RCPs, RCP2.6, RCP4.5, RCP6, and RCP8.5, are named

after a possible range of radiative forcing values in the year 2100 relative to pre-industrial

values (+2.6, +4.5, +6.0, and +8.5 W/m2, respectively).[2]


• Representative Concentration Pathways (RCP) 4.5 Low-medium emissions increasing scenario • Representative Concentration Pathways (RCP) 8.5

Fossil fuel intensive scenario

RCP 8.5

RCP 4.5

Global Climate Simulation Scenarios

RCP:20052100

Source: http://stratus.astr.ucl.ac.be/textbook/pdf/Chapter_6.pdf


Projections of global average warming

By the end of the century, the increase of global mean surface temperature above 1986-2005 levels is

projected to be:

0.3-1.7˚C for RCP2.6

2.6-4.8˚C for RCP8.5


Warming will not be the same everywhere

• There is very high confidence that long-term warming will be larger over land than over the

ocean, and that the Arctic region will warm most rapidly.

• Ocean warming will continue for centuries, even if greenhouse gas emissions are

decreased.


There will be large geographical variations in precipitation

change

• For the next few decades, changes in regional-scale precipitation will be

strongly influenced by natural variability.

• Contrast between wet and dry regions and seasons will increase over most of

the globe, though there are regional exceptions.

• Monsoon precipitation is likely to intensify, along with a lengthening of the

monsoon season. • Extreme precipitation events over most of the mid-latitude land masses and over wet tropical regions will

be very likely to become more intense and more frequent by the end of this century. • Monsoon precipitation is likely to intensify, along with a lengthening of the monsoon season.



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Part 4: Conclusion and Key

Uncertainties


Conclusion

• Continued emission of greenhouse gases will cause further

warming and changes in all components of the climate system.

Limiting climate change will require substantial and sustained

reductions of greenhouse gas emissions.

• Cumulative emission of CO2 largely determine global mean surface

warming by the late 21st century and beyond. Most aspects of

climate change will persist for many centuries even if emissions of

CO2 are stopped. This represents a substantial multi-century

climate change commitment created by past, present and future

emissions of CO2.


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THANK YOU

[email protected]


© Crown copyright Met

Office

Impacts Climate

scenarios Atmospheric

concentrations

Emissions scenarios

Socio-economic scenarios

SRES: Sequential approach to developing

climate scenarios

• Climate modellers await results from socio-economic

modellers

• Emissions scenarios chosen early on are restrictive.. E.g.

no exploration of deliberate mitigation strategies, difficult

to explore uncertainties in carbon cycle feedbacks.


© Crown copyright Met

Office

RCPs: Parallel approach to generating climate

scenarios

Impacts

Emissions scenarios

Atmospheric concentrations (‘Representative Concentration Pathway’, RCPs)

Climate scenarios Integrated assessment

modellers and climate

modellers work simultaneously and

collaboratively

Socio-economics

Policy Intervention (mitigation or adaptation)

Carbon cycle and atmospheric chemistry

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1. Update on the 5th Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC)

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