Planning for Climate Change - UN-Habitat

Climate Change: A Review
3.0 Climate Change: A Review
This section explains, in basic terms, the challenges generated by climate change.
The Challenge of Climate Change provides a summary review of how and why climate
change is affecting our planet’s atmosphere and the biophysical cycles driven by it –
water and air temperatures, weather, tides, etc. This sub-section summarizes the most
relevant and important information in the extensive and often overwhelming body of
data and research around climate change.
Cities and Climate Change explains how the biophysical challenges generated by
climate change in turn generate very real and growing impacts on cities and towns
and, most importantly, the people that live there. This sub-section explains how these
impacts can affect vulnerable groups – the poor, women, children, etc. – more severely,
and explains where, how and through what policy and program avenues planners
can play a role in responding to these impacts, preparing for future potentials, and
mitigating a city’s greenhouse gas emissions.
3.1 THE CHALLENGE OF CLIMATE CHANGE
Climate change refers to changes to the average weather or weather variability of a
region or the planet over time. It is measured by changes in temperature, precipitation,
wind, storms and other weather indicators.
The key climate change indicator that scientists look to is the average surface
temperature of the earth. Over the past 50 years, the global average temperature trend
increased by 0.65°C. Global ocean temperature is also an important factor to consider
due to its affect on surface temperatures. The world’s oceans are absorbing much of
heat added to the earth’s climate system and as the ocean circulates, much of that heat
is released into the atmosphere, increasing the warming effect over time. No regions are
immune to rising temperatures, though some have witnessed sharper increases in the
last 25 years.
In its 4th Assessment Report in 2007, the Intergovernmental Panel on Climate Change
(IPCC) stated that, “Most of the observed increase in global average temperatures
since the mid-20th century is very likely (>90%) due to the observed increase in
anthropogenic greenhouse gas concentrations.” The increase in carbon dioxide levels
in the atmosphere – primarily from the burning of fossil fuels and land use change – is
increasing global temperatures at a rate never before seen in human history.
A Strategic, Values-based Approach for Urban Planners
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