The Importance of Time Scales

Two main types of interventions are often discussed as ways to reduce the impacts of climate change on society: mitigation and adaptation. Mitigation is a reduction in greenhouse gas emissions, which leads (eventually) to a reduction in climate change. Adaptation refers to changes made to a system impacted by climate, in this case some aspect of the food economy, that improve the outcome of climate change relative to no adaptation. Adaptations can include both changes that either reduce negative outcomes or enhance positive outcomes.

The effectiveness of an intervention can be extremely dependent on the time scale of interest (Fig. 1.2). For example, investments in adaptation are the only real way of reducing impacts for the next 30-40 years, because the benefits of mitigation are realized with a lag of roughly this length (see Chapter 2). However, nearly all assessments agree that adaptations are less effective than mitigation for reducing impacts by 2100.

Much of this book will focus on time scales of the next few decades, rather than the end of the century. There are several pragmatic reasons for this choice. First, growth in food demand is expected to be faster before 2050 than after, because global population growth will likely decelerate. According to the United Nations' medium growth rate scenario, for instance, population will increase by 2.8 billion people between 2000 and 2050 but only by 0.2 billion between 2050 and 2100 (Table 1.1). The challenges to food security of rising global demand are therefore

Fig. 1.2 A schematic view of the effectiveness of adaptation and mitigation as a function of time

Table 1.1 Projections of global population (billions of people) to 2050 and 2100 for different growth scenarios (data source: United Nations Population Division 2004)

Fig. 1.2 A schematic view of the effectiveness of adaptation and mitigation as a function of time

2020 2040 2060 2080 2100

2020 2040 2060 2080 2100

Year

Low variant

Medium variant

High variant

2000 2050 2100

likely to be greatest in the near-term. Put differently, the challenge of the next few decades is to foster a tremendous growth in agricultural production in the face of climate change in order to improve food security, while after 2050 lies the more modest challenge of maintaining existing production levels in a warming world.

A second and no less important reason is that uncertainties in projections beyond 2050 are far greater than those of the next few decades. That is, it makes sense to focus on the aspects of the problem where projections are most likely to be accurate. Beyond 2050, agricultural technologies may be completely different from the current ones, and temperatures at a given location will often be beyond anything currently experienced (Chapter 2), making projections of climate impacts on agriculture very difficult.

Third, our experience is that most decisions, whether made in public or private sectors, do not account for time scales beyond a few decades. Therefore, scientific assessments of the near-term are likely to have a greater impact on societal choices than are those focused on the end of the twenty-first century, even if the latter would play a greater role in an ideal world.

Finally, and perhaps most importantly, is the fact that food security impacts of climate change in the next few decades may be severe in some locations. There is tremendous need for science that supports effective adaptations, especially when considering that most investments in agriculture take over a decade to provide substantial returns. Efforts to adapt to climate in 2020 or 2030 must therefore begin soon. There are obviously larger potential impacts as one looks beyond 2050, but one need look no further than the next 20 years to find a major scientific and societal challenge.

Although we believe these reasons are compelling enough to justify a focus on the short-term, we recognize that a view of the longer term is also needed, if only for the critical job of assessing the eventual benefits of mitigation. We therefore also include many references to assessments of 2080-2100, although none to our knowledge extend beyond this time.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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