Topics: Greenhouse gas, Intergovernmental Panel on Climate Change, IPCC Fourth Assessment Report Pages: 6 (822 words) Published: October 19, 2013
UNIB10007 Introduction to Climate Change

Climate change: Is there a problem?
Professor David Karoly
School of Earth Sciences, University of Melbourne

Some views from leaders
• Ban Ki Moon “Climate change is the greatest threat
facing humanity. It threatens to undo 50 years of our
development work and it will impact the poor in the
greatest sense.”
• Barack Obama “We will respond to the threat of
climate change, knowing that the failure to do so
would betray our children and future generations.”
• Kevin Rudd: Climate change is “the greatest moral,
economic and social challenge of our time”

Intergovernmental Panel
on Climate Change (IPCC)
•  Joint body of UN Environment Program and World
Meteorological Organization, established in 1988
•  Every 5-6 years, carries out a comprehensive assessment of climate change science, impacts, and approaches for
mitigation and adaptation to climate change
•  Includes representatives from all countries
•  Fourth Assessment Report prepared by more than 500
scientists over the last three years
•  Summaries for Policy Makers approved by consensus
(including representatives of the Australian govt) at meetings in Paris (Feb 07), Brussels (Apr 07) and Bangkok (May 07)
•  Received the 2007 Nobel Peace Prize jointly with Al Gore

IPCC Fourth Assessment Report 2007
•  ‘Warming of the climate system is unequivocal’
•  ‘Most of the observed increase in global average
temperatures since the mid-20th century is very
likely due to the observed increase in anthropogenic
greenhouse gas concentrations’
•  ‘Continued greenhouse gas emissions at or above
current rates would cause further warming and
induce many changes in the global climate system
during the 21st century that would very likely be
larger than those observed during the 20th century’
•  ‘21st century anthropogenic CO2 emissions will
contribute to warming and sea level rise for more
than a millennium, due to the long timescales
required for removal of this gas’

Global mean temperature to 2012

Global ocean heat content change

Indicators of global warming
(from “State of the Climate 2009”, Bull Am Met Soc, 2010)

Greenhouse gas concentrations

Concentrations in 2011
CO2 = 390 ppm, CO2-e = 473 ppm


Causes of

Observed and modeled minimum Arctic
sea-ice extent in September

Projected climate
change hotspots
in Australia
(from IPCC AR4
WGII, chapt 11)

Global CO2 Emissions from Fossil Fuels

Who has caused the problem?

UNFCCC includes principle that: “Parties should protect the climate system...on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities. Accordingly, the developed country Parties should take the lead in combating climate change” (UNFCCC, Art.3.1). Regional greenhouse gas emissions in 2004

Budget approach
Cumulative emissions
allowed for 25% risk of
exceeding 2°C
•  Equal per capita
emissions allowance
•  Global budget of
1000Gt CO2 until 2050
•  For world population of
7G, 140 t CO2 per
capita budget until 2050
•  For Aust emissions of
19 t CO2 per person
from fossil fuels, budget
is used in about 7 years
Fig 5.1, The Science of Climate
Change, AAS 2010

The Critical Decade: Key messages (2011)

Australian Climate Commission
• There is no doubt that the climate is changing. The
evidence is overwhelming and clear.
• We are already seeing the social, economic and
environmental impacts of a changing climate.
• It is beyond reasonable doubt that human activities – the burning of fossil fuels and deforestation – are
triggering the changes we are witnessing in the global
• This is the critical decade. Decisions we make from
now to 2020 will determine the severity of climate
change our children and grandchildren experience.
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