在2014年6月28日的托福阅读考试中有这样一道题：地球能源循环系统。出国留学网(www.liuxue86.com)小编提醒大家：分类型文章，需要关注各分类项目下的内容条目。用结构化阅读的方法做好笔记，最后的主旨题比较容易从正向选出，节省宝贵时间。
托福阅读真题再现：
地球能源循环系统
讲的是那个地球能源有内部能源和外部能源。
主要收集太阳光照(占了地球能源很大比例)
还做了对比说人类所消耗的能源是什么什么数(与地球内部能源比起来微不足道)(这有老师问为什么提人类消耗的能源)
有一段讲月亮与地球之间的牵引导致了潮汐(这也有考题 问月亮对地球的影响 有一个超级逗比的模糊选项说月球导致地球潮汐之后使得地球上的海岸线重新形成。。。)
还有一段讲的是云啊什么的作用 在说明地球没有全部吸引光能 40%被折射回去 吸收的之后各种转化 最后又回到太空。
这里有几道：1. 如果云多了地球会怎样 答案一定是反射回去的能量多了呗
2. 吸收的过程是怎么样的 答案应该是复杂的
貌似2. 是个单词题
解析：此类分类型文章，需要关注各分类项目下的内容条目。用结构化阅读的方法做好笔记，最后的主旨题比较容易从正向选出，节省宝贵时间。
相关背景：
Earth's energy budget
[From Wikipedia, the free encyclopedia]
Earth's climate is largely determined by the planet's energy budget, i.e., the balance of incoming and outgoing radiation. It is measured by satellites and shown in W/m2.
Earth's energy budget or Earth's radiation balance, describes the net flow of energy into Earth in the form of shortwave radiation and the outgoing infrared radiation out to space.
The Earth's equilibrium surface temperature is defined by radiative equilibrium, the balance between the incident and outgoing radiation budget. Climate change is defined by changes in Earth's energy budget.
Outgoing, longwave flux radiation at the top-of-atmosphere (Jan 26-27, 2012). Heat energy radiated from Earth (in watts per square meter) is shown in shades of yellow, red, blue and white. The brightest-yellow areas are the hottest and are emitting the most energy out to space, while the dark blue areas and the bright white clouds are much colder, emitting the least energy.
Received radiation is unevenly distributed over the planet, because the Sun heats equatorial regions more than polar regions. Earth’s heat engine, are the coupled processes of the atmosphere and hydrosphere to even out solar heating imbalances through evaporation of surface water, convection, rainfall, winds, and ocean circulation. The Earth's energy balance will depend on many factors, with the incident absorption varying with atmospheric and surface factors including cloud cover (albedo), snow cover, atmospheric aerosols, and vegetation and land use patterns, and the outgoing radiation also varying with atmospheric and surface emissivity. These factors all vary with time.
Changes in surface temperature due to Earth's energy budget changes do not occur instantaneously, due to the inertia (slow response) of the oceans and cryosphere to react to the new energy budget. The net heat flux is buffered primarily in the ocean heat content, until a new equilibrium state is established between incoming and outgoing radiative forcing and climate response.
When the amount of the solar energy reaching Earth equals the thermal energy amount being radiated out, the radiative forcings are in a state of radiative equilibrium or balance.
托福阅读背景知识：地球能源循环系统
Incoming radiant energy (shortwave)
The total amount of energy received by Earth's atmosphere is normally measured in watts and determined by the solar constant. Earth incoming solar radiation depends on day-night cycles and the angle at which sun rays strike, thus calculated by its cross section and distribution on the planets surface, calculated with 4·π·RE2, in sum one-fourth the solar constant (approximately 340 W/m2, plus or minus 2 W/m2). Since the absorption varies with location as well as with diurnal, seasonal, and annual variations, numbers quoted are long-term averages, typically averaged from multiple satellite measurements.
Of the ~340 W/m2 of incident solar radiation intercepted by the Earth, an average of ~77 W/m2 is reflected back to space by clouds and the atmosphere and ~23 W/m2 is reflected by the surface albedo, leaving about 240 W/m2 of solar energy input to the Earth's energy budget.
Earth's internal heat and other small effects
The geothermal heat flux from the Earth's interior is estimated to be 47 terawatts. This comes to 0.087 watt/square meter, which represents only 0.027% of Earth's total energy budget at the surface, which is dominated by 173,000 terawatts of incoming solar radiation.
There are other minor sources of energy that are usually ignored in these calculations: accretion of interplanetary dust and solar wind, light from distant stars, the thermal radiation of space. Although these are now known to be negligibly small, this was not always obvious: Joseph Fourier initially thought radiation from deep space was significant when he discussed the Earth's energy budget in a paper often cited as the first on the greenhouse effect.
Outgoing radiant energy (longwave)
Of the incident solar energy, about 77 W/m2 is absorbed in the atmosphere, and the remainder by the surface (both land and ocean). Heat energy is then transported between surface, ocean, and atmosphere by infrared radiated by the planet surface layers (land and ocean) to the atmosphere, and from the atmosphere to the surface; and transported via evapotranspiration (84.4 W/m2, the latent heat) or conduction/convection (18.4 W/m2) processes. Ultimately, the energy is then radiated in the form of thermal infrared radiation back into space.
Earth's energy imbalance
If the incoming energy flux is not equal to the outgoing thermal (infrared) radiation, the result is an energy imbalance, resulting in net heat added to the planet (if the incoming flux is larger than the outgoing). Earth's Energy Imbalance measurements provided by Argo floats detected accumulation of ocean heat content (OHC) in the recent decade. The estimated imbalance is 0.58± 0.15 W/m2.
Several satellites have been launched into Earth's orbit that indirectly measure the energy absorbed and radiated by Earth, and by inference the energy imbalance. The NASA Earth Radiation Budget Experiment (ERBE) project involves three such satellites: the Earth Radiation Budget Satellite (ERBS), launched October 1984; NOAA-9, launched December 1984; and NOAA-10, launched September 1986.
Today the NASA satellite instruments, provided by CERES, part of the NASA's Earth Observing System (EOS), are especially designed to measure both solar-reflected and Earth-emitted radiation from the top of the atmosphere (TOA) to the Earth's surface.
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