Mid Twenty-first Century Research Articles

Combined heat-and-power implementation in the UK: Past, present and prospective developments

The world is insufficiently concerned with ensuring its long-term energy supplies. For instance, a severe reduction of the availability of cheap fossil fuels is likely to occur in the mid twenty-first century. However, there are several steps that could be taken in the UK to ensure the sustainability of adequate power supplies (e.g. a Severn Barrage tidal-power harnessing system capable of satisfying ∼8% of the electricity needs of the UK; a national campaign for the implementation, where economic, of combined heat-and-power (CHP) installations). The implementation of CHP technology is, even now, frequently an economically justifiable option which is capable of providing highly efficient, environmentally friendlier electricity and heat supplies. A variety of fuels, including oil, coal, natural gas, refuse, sewage, nuclear power and renewables, can be used as the energy source. Despite being thermodynamically attractive, the pace of adoption of CHP in the UK has been disappointingly slow. An historical record of the evolution of CHP as well as community (district) heating (DH) in the UK is presented. Recent developments and a possible future scenario for energy supplies, affecting the rate of adoption of CHP-DH systems in the UK, are outlined.

Climate change and the response of forests

Abstract The global climate has warmed by over 0·5°C during the last 125 years. Models of the Earth's temperature reponse to increasing levels of atmospheric carbon dioxide and other greenhouse gases estimate that the average global surface temperature will rise about 4°C by the mid twenty-first century. High latitudes will warm more than lower latitudes and winters more than summers. Forests will undergo enormous changes as temperatures increase and precipitation patterns shift. It is doubtful that forest movement will meet the rate of climate change. Many sensitive hardwood tree species, such as paper and yellow birch, sugar maple and black ash, may die. Boreal forests will replace tundra and mixed hardwood forests will replace them. Much of the change expected in the location and composition of forests may be detected by means of remote sensing.

When Is a Burden Not a Burden? The Elderly in America

Henry J. Aaron rHE PROBLEMS of supporting an aging population are arousing in creasing concern in many developed nations. A cursory glance at demo graphic statistics and projections reveals the reason. The proportion of the population over age 65 is expected at least to double in many developed nations over the period from 1950 to 2020 (see table 1). The timing and size of this increase vary in important ways from nation to nation, but the pattern is universal. The ultimate ratio of the aged to total population, which depends only on birth and mortality rates, will be reached only in the mid twenty-first century and differs little from country to country. In this paper, I shall suggest that the burdens imposed by an increasing aged population, defined as persons 65 or older, are exaggerated, but that the problems created by the growth in the number of the very old, arbitrarily defined as per sons 80 or older, should cause greater concern than they do.