Global Warming Is 300-Year-Old News

Text 2

Text 1

How Serious a Threat is Climate Change?

There is now a consensus among the majority of the world’s scientists that the Earth is already experiencing the effects of man-made climate change.

Climate change is caused by emissions of pollutants which increase the so called ‘greenhouse effect’, by which gases in the atmosphere create a ‘blanket’ or warming effect by limiting the ability of heat to be radiated out into space. Gases responsible for the greenhouse effect inclued water vapour, carbon dioxide, methane, ozone and halocarbons, the latter four of which have been affected by human activities over the last 300 years. Concentrations of carbon dioxide (from burning of coal, oil and gas, and land-use changes), methane (from agriculture and natural gas leakage), and ozone in the lower atmosphere (from the products of vehicle exhausts) have increases greatly over this period.

Careful analysis of the historical record of measurements shows that global temperature has risen by about 0.6° C since the beginning of the twentieth century, with about 0.4° C of this warming occurring since the 1970s. The year 1998 was the warmest in this 142-year recode, and 2001 was the third warmest. Globally, the decade of the 1990s was the warmest in the last 100 years, and it is likely the last 100 years was the warmest century in the last millennium.

Greenhouse gases are likely to be emitted in large quantities for the foreseeable future. The result will be a substantially altered climate. Sophisticated computer simulation models show that the global mean temperature is likely to rise by between 1.5 and 5.9° C by 2100. The wide range in this estimate reflects both uncertainties in how the climate will respond to increased concentrations of greenhouse gases and the fact that we simply don’t know how emissions of greenhouse gases will change in the coming decades. How much we do emit will depend on our choices as a global society over the coming years and decades.

Around the world, the land is likely to warm more than the ocean, and northern high latitudes will warm the most. Global precipitation is likely to increase by about 2% per degree of warming, but the regional patterns are complicated and not well-understood – many areas will see significant drying while others will get substantially wetter.

One major consequence of climate change will be continuing sea-level rise, and accompanying increase in the occurrence of extreme storm surges. Many millions of people live in areas at risk from inundation. Changing rainfall patters are likely to increase soil erosion and subsidence, and profoundly affect water availability and quality. Drier soils will change the type and yield of crops, increasing the risk of famine in some areas. Health is likely to be affected, both directly (more summer heat stress but fewer cold deaths in winter) and indirectly (through changes in diseases such as increased food poisoning). Infectious diseases such as malaria are expected to spread. Evidence is therefore accumulating that climate change is under way and that something needs to be done now if we are to mitigate its future effects.

However, carbon dioxide has a very long lifetime in the atmosphere and we have already significantly increased levels of greenhouse gases in the atmosphere above their pre-industrial levels. We are already committed to a certain amount of climate change over the next 100 years, and we must expect to have to deal with impacts that have yet to be manifested: we need to address adaptation as well as mitigation.

Climate Change News from BBC

www.bbc.co.uk/science/hottopics/climatechange

Kyoto supporters cheer new findings that the Earth’s surface temperature is

probably rising. But this trend isn’t recent and isn’t manmade.

Opponents of the use of coal, oil and natural gas – the World’s primary energy sources – received what looked to be good news last week. A National Research Council panel of 11 members, after reviewing and evaluating existing experimental data over the last 20 years, concluded that there has probably been a rise in the Earth’s surface temperature.

Unfortunately for advocates of the Kyoto treaty, atmospheric temperatures over the same two decades have not risen. The climate model chosen to support the Kyoto plan – a scheme to sharply reduce energy use – predicts that atmospheric temperature should have risen by one degree to two degrees Fahrenheit over those 20 years. Yet satellites and weather balloons have shown no verifiable atmospheric temperature rise.

Indeed, despite the hype, the NRC findings do little to advance the argument that people have caused global warming. The NRC panel’s 85-page report, though concluding that surface temperature has risen a little, is full of inconclusive results. The first sentence of the report’s concluding remarks reads: “The various kinds of evidence examined by the panel led it to conclude that the observed disparity between the surface and lower- to mid-tropospheric (atmospheric) temperature trends during this particular 20-year period is probably at least partially read. ” (Italics added.)

The report further says that uncertainties in all of the records – surface, satellite and balloon – are too great to draw conclusions about the relative effects of volcanic eruptions, measurement errors due to localized human activity in urban areas, instrument errors, human release of greenhouse gases and other factors. The report concludes that “major advances” in scientific methods will be necessary before these questions can be resolved.

Дата добавления: 2014-11-16