Evidence suggests that the Earth’s atmosphere is warming owing to increases in human-made emissions of greenhouse gases (GHG), primarily carbon dioxide (CO2). Atmospheric CO2 concentrations have increased by almost 100 ppm (parts per million) since their preindustrial level, reaching 379 ppm in 2005.1 (IPCC, 2007). Global mean temperatures have risen by 0.74ºC over the past century, with 0.4ºC of this increase occurring since the 1970s. Mitigation – that is, reducing the amount of GHG (greenhouse gas) emissions that we produce – is critical to tackling climate change (see Box 1, on page 2). However, it appears that some degree of climate change has already begun. Extreme weather in recent years has disrupted and damaged urban transport systems: flooding, heat waves and storms have all led to delays and increased costs. An urgent task facing us is how we adapt existing transport planning, design, construction and maintenance – and decisions we make about how we travel – to climate change.
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