翻译实习.docx

1、翻译实习Climate changeClimate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., mo

2、re or fewer extreme weather events). Climate change is caused by factors that include oceanic processes (such as oceanic circulation), variations in solar radiation received by Earth, plate tectonics and volcanic eruptions, and human-induced alterations of the natural world; these latter effects are

3、 currently causing global warming, and climate change is often used to describe human-specific impacts.Scientists actively work to understand past and future climate by using observations and theoretical models. Borehole temperature profiles, ice cores, floral and faunal records, glacial and perigla

4、cial processes, stable isotope and other sediment analyses, and sea level records serve to provide a climate record that spans the geologic past. More recent data are provided by the instrumental record. Physically-based general circulation models are often used in theoretical approaches to match pa

5、st climate data, make future projections, and link causes and effects in climate change.1.TerminologyThe most general definition of climate change is a change in the statistical properties of the climate system when considered over long periods of time, regardless of cause. Accordingly, fluctuations

6、 over periods shorter than a few decades, such as El Nio, do not represent climate change.The term sometimes is used to refer specifically to climate change caused by human activity, as opposed to changes in climate that may have resulted as part of Earths natural processes. In this sense, especiall

7、y in the context of environmental policy, the term climate change has become synonymous with anthropogenic global warming. Within scientific journals, global warming refers to surface temperature increases while climate change includes global warming and everything else that increasing greenhouse ga

8、s levels will affect.2.CausesOn the broadest scale, the rate at which energy is received from the sun and the rate at which it is lost to space determine the equilibrium temperature and climate of Earth. This energy is distributed around the globe by winds, ocean currents, and other mechanisms to af

9、fect the climates of different regions.Factors that can shape climate are called climate forcings or forcing mechanisms.These include processes such as variations in solar radiation, deviations in the Earths orbit, mountain-building and continental drift, and changes in greenhouse gas concentrations

10、. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcings, while others respond more quickly.Forcing mechanisms can be either internal or

11、 external. Internal forcing mechanisms are natural processes within the climate system itself (e.g., the thermohaline circulation). External forcing mechanisms can be either natural (e.g., changes in solar output) or anthropogenic (e.g., increased emissions of greenhouse gases).Whether the initial f

12、orcing mechanism is internal or external, the response of the climate system might be fast (e.g., a sudden cooling due to airborne volcanic ash reflecting sunlight), slow (e.g. thermal expansion of warming ocean water), or a combination (e.g., sudden loss of albedo in the arctic ocean as sea ice mel

13、ts, followed by more gradual thermal expansion of the water). Therefore, the climate system can respond abruptly, but the full response to forcing mechanisms might not be fully developed for centuries or even longer.2.1 Internal forcing mechanismsNatural changes in the components of earths climate s

14、ystem and their interactions are the cause of internal climate variability, or internal forcings. Scientists generally define the five components of earths climate system to include Atmosphere, hydrosphere, cryosphere, lithosphere (restricted to the surface soils, rocks, and sediments), and biospher

15、e.2.1.1 Ocean variabilityThe ocean is a fundamental part of the climate system, some changes in it occurring at longer timescales than in the atmosphere, massing hundreds of times more and having very high thermal inertia (such as the ocean depths still lagging today in temperature adjustment from t

16、he Little Ice Age). Short-term fluctuations (years to a few decades) such as the El Nio-Southern Oscillation, the Pacific decadal oscillation, the North Atlantic oscillation, and the Arctic oscillation, represent climate variability rather than climate change. On longer time scales, alterations to o

17、cean processes such as thermohaline circulation play a key role in redistributing heat by carrying out a very slow and extremely deep movement of water, and the long-term redistribution of heat in the worlds oceans.A schematic of modern thermohaline circulation. Tens of millions of years ago, contin

18、ental plate movement formed a land-free gap around Antarctica, allowing formation of the ACC which keeps warm waters away from Antarctica.2.2 External forcing mechanismsIncrease in atmospheric CO2 levelsMilankovitch cycles from 800,000 years ago in the past to 800,000 years in the future.Variations

19、in CO2, temperature and dust from the Vostok ice core over the last 450,000 years2.2.1Orbital variationsMain article: Milankovitch cyclesSlight variations in Earths orbit lead to changes in the seasonal distribution of sunlight reaching the Earths surface and how it is distributed across the globe.

20、There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of orbital variations are variations in Earths eccentricity, changes in the tilt angle of Earths axis of rotation, and precessio

21、n of Earths axis. Combined together, these produce Milankovitch cycles which have a large impact on climate and are notable for their correlation to glacial and interglacial periods,7 their correlation with the advance and retreat of the Sahara,7 and for their appearance in the stratigraphic record.

22、8The IPCC notes that Milankovitch cycles drove the ice age cycles; CO2 followed temperature change with a lag of some hundreds of years; and that as a feedback amplified temperature change.9 The depths of the ocean have a lag time in changing temperature (thermal inertia on such scale). Upon seawate

23、r temperature change, the solubility of CO2 in the oceans changed, as well as other factors impacting air-sea CO2 exchange. 2.2.2 Solar outputMain article: Solar variationVariations in solar activity during the last several centuries based on observations of sunspots and beryllium isotopes. The peri

24、od of extraordinarily few sunspots in the late 17th century was the Maunder Minimum.The sun is the predominant source for energy input to the Earth. Both long- and short-term variations in solar intensity are known to affect global climate.Three to four billion years ago the sun emitted only 70% as

25、much power as it does today. If the atmospheric composition had been the same as today, liquid water should not have existed on Earth. However, there is evidence for the presence of water on the early Earth, in the Hadean1112 and Archean1311 eons, leading to what is known as the faint young Sun para

26、dox.14 Hypothesized solutions to this paradox include a vastly different atmosphere, with much higher concentrations of greenhouse gases than currently exist.15 Over the following approximately 4 billion years, the energy output of the sun increased and atmospheric composition changed. The Great Oxy

27、genation Event oxygenation of the atmosphere around 2.4 billion years ago was the most notable alteration. Over the next five billion years the suns ultimate death as it becomes a red giant and then a white dwarf will have large effects on climate, with the red giant phase possibly ending any life o

28、n Earth that survives until that time.Solar output also varies on shorter time scales, including the 11-year solar cycle16 and longer-term modulations.17 Solar intensity variations are considered to have been influential in triggering the Little Ice Age,18 and some of the warming observed from 1900

29、to 1950. The cyclical nature of the suns energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves. Research indicates that solar variability has had effects including the Maunder Minimum from 1645 to 1715 A.D., part of th

30、e Little Ice Age from 1550 to 1850 A.D. which was marked by relative cooling and greater glacier extent than the centuries before and afterward.1920 Some studies point toward solar radiation increases from cyclical sunspot activity affecting global warming, and climate may be influenced by the sum o

31、f all effects (solar variation, anthropogenic radiative forcings, etc.). Interestingly, a 2010 study23 suggests, “that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations.”In an Aug 2011 Press Release,24 CERN announced the publication in

32、the Nature journal the initial results from its CLOUD experiment. The results indicate that ionisation from cosmic rays significantly enhances aerosol formation in the presence of sulphuric acid and water, but in the lower atmosphere where ammonia is also required, this is insufficient to account for aerosol formation and additional trace vapours must be involved. The next step is to find more about these trace vapours, including whether they are of natural or human origin.2.2.3 VolcanismIn atmospheric temperature from 1979 to 2010, determined by MSU NASA sa