12.2 第6次大规模灭绝:人类
章节大纲
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The geological record contains information about the dramatic changes that have occurred on our planet. The lessons from the five known mass extinctions show that the impact to climate and life is greatest when change is more sudden.
::地质记录载有地球发生的巨大变化的信息。 五个已知大规模灭绝的教训显示,当变化更加突然时,对气候和生命的影响最大。During the middle to late Cretaceous period the overall temperature of the Earth increased by 5 °C. However, this change took place slowly, over the course of millions of years. The warming is thought to have been caused by the steady release of greenhouse gases from volcanic eruptions. Because the rate was so slow, the oceans were able to absorb the greenhouse gases without causing significant acidification. As a result, most life was able to adapt or migrate and survive.
::然而,这一变化在数以百万计的时间内缓慢地发生。 据认为,变暖是由于火山爆发中温室气体的不断释放造成的。由于速度太慢,海洋能够吸收温室气体,而不会造成重大酸化。 结果,大多数生命得以适应或迁移并生存。In contrast , during the Palocene-Eocene thermal maximum (PETM) temperatures rose by 0.025 °C every 100 years. I n just a few thousand years, the temperature had increased by 5 °C . The warming was caused by a combination of volcanoes, methane release from the seafloor, and peat/coal fires. As heating progressed, the permafrost began to thaw, leading to the release of even more greenhouse gases. The oceans began to acidify, leading to the extinction of many organisms living on the seafloor.
::相反,在Palocene-Eenne热最高温度(PETM)每100年上升0.025°C,仅在几千年中温度就上升了5°C。 升温是由火山、海底甲烷排放和泥炭/煤炭大火的结合造成的。 随着加热的进展,永久冻土开始融化,导致更多的温室气体释放。 海洋开始酸化,导致生活在海底的许多生物灭绝。Today, humans are exerting a pressure on the Earth system so extreme that it is triggering the start of a new geological epoch : the Anthropocene. Modern-day global warming appears to be occurring at a rate of 1-4 °C per 100 years, orders of magnitude faster than the rate during the PETM. The Earth is expected to gain 2-10 °C in the next 100 years. There have been times in the history of the Earth when there was as much - or perhaps more - carbon in the atmosphere. There has probably never been a time in the past 4.5 billion years when the rate of change of carbon in the atmosphere has been so rapid. We have pulled coal from the carboniferous period out of the ground and we are burning it to fuel our industrial revolution. L ike it or not, o ur mark will be left in the geological record of out planet; the first stage of a mass extinction, a rapid , has already started .
::今天,人类正在对地球系统施加如此巨大的压力,以至于它正在触发一个新的地质时代的开始:人类。现代全球升温似乎以每100年1-4°C的速度发生,其规模速度比PETM期间的速度快。预计地球在未来100年将增加2-10°C。在地球历史上,曾经有几次在大气中存在同样多或可能更多的碳。在过去45亿年中,大气中的碳变化速度可能从未如此迅速。我们已经从地上提取煤炭,正在燃烧煤炭,以刺激我们的工业革命。和现在一样,我们的标记将留在地球外的地质记录中;大规模灭绝的第一阶段,即快速的,已经开始。The sixth extinction
::第6次灭绝Since the industrial revolution, we have had a front- row seat to the sixth major mass extinction. Human activity has led to widespread habitat loss, climate change, pollution, and rising ocean acidity. Vertebrates are dying out at a rate estimate to be a hundred times faster than they would be without human interference.
::自工业革命以来,我们拥有了第六大大规模灭绝的前排席位。 人类活动导致了广泛的生境损失、气候变化、污染和海洋酸度上升。 高血压的死亡率估计比人类干预速度快一百倍。Amphibians that interact with polluted land and water are most impacted, with a current extinction rate tens of thousands times greater than the background extinction rate. Rising temperatures are threatening most species with changes that are now happening on the timescale of generations rather than thousands of millions of years as before.
::与被污染的土地和水相互作用的两栖动物受到的影响最大,目前的灭绝率比背景灭绝率高出数万倍。 气温上升正在威胁着大多数物种,这些变化正在几代人的时间范围内发生,而不是上百万年前的数千万年。The Energy Budget for Earth climate
::地球气候能源预算A n "airless Earth" will absorb higher energy photons from the Sun in the top 1-meter of soil and then re-radiate that energy back into space in the form of infrared radiation. The incoming energy comes from a 5500 K black body - the Sun - and an airless Earth would radiate as a blackbody with a temperature of about 253 K .
::“无空气地球”将在土壤的顶部1米内吸收太阳的较高能量光子,然后以红外辐射的形式将能量重新辐射回空间。 能量来自5500K黑体 — — 太阳 — — 无空气的地球会像黑体一样辐射,温度约为253K。The energy from the Sun peaks at optical wavelengths and would be absorbed and re-emitted by an airless Earth as infrared wavelengths. Recall that the Sun and Earth will emit as black bodies with a peak wavelength that is inversely proportional to their effective temperature.
::太阳的能量以光波长为顶峰,无空气的地球将吸收和再排放为红外波长。 回顾太阳和地球将以黑体的形式排放,峰值波长与其有效温度成反比。However, it is more difficult for the incoming solar energy to escape when the Earth has an atmosphere. Molecules with three atoms are particularly effective at absorbing the infrared radiation released from the surface of the Earth. The absorbed energy is transformed into energy for vibrating and bending the molecular bonds of these greenhouse gases, as shown in the short TED-Ed video below.
::然而,当地球有大气层时,即将到来的太阳能就更难逃脱。 有三个原子的微粒在吸收地球表面释放的红外线辐射方面特别有效。 吸收的能量转化为振动和弯曲这些温室气体的分子联结的能量,如下面TED-Ed短片所示。Ultimately, energy is re-emitted and adds heat into the atmosphere. The energy budget (incoming higher frequency solar energy and absorbed-released lower frequency energy) is summarized in the image below. Not all of what comes in is released again.
::最终,能源是再排放的,并将热量添加到大气中。 能源预算(通过高频太阳能和吸收释放的低频能源)在下面的图像中进行了总结。 并不是所有的能源都再次释放出来。The energy budget of the Earth, including greenhouse gases.
::包括温室气体在内的地球能源预算。The solar flux above the Earth's atmosphere is 1360 Watts per square meter. However, only one hemisphere of the Earth faces the Sun. F urthermore, the surface of the Earth is curved not flat, so there is a geometric reduction, such that an average of 340 Watts per square meters is intercepted above the atmosphere over the entire surface of the Earth. Without greenhouse warming from the Earth's atmosphere, our planet would be a frozen world. The presence of methane, water, carbon dioxide, and other natural greenhouse gases transformed the Earth to a habitable world with oceans of liquid water.
::地球大气层上空的太阳通量是每平方米1360瓦特,然而,地球只有一个半球面对太阳。此外,地球表面的曲线不是平的,因此进行了几何缩减,因此在整个地球表面的大气层上空平均截获每平方米340瓦特。没有地球大气层的温室变暖,我们的地球将是一个冰冻的世界。甲烷、水、二氧化碳和其他天然温室气体的存在,使地球变成一个有液体水的可居住世界。Anthropogenic climate change
::人为气候变化In 1896, the Swedish scientist Svante Arrhenius calculated that the burning of coal by humans would add carbon dioxide to the atmosphere caus ing a small amount of warming. This was a curiosity, but it was hard to imagine that the then-world population of 1.6 billion people would have much impact. By the 1930s, the precise monitoring of climate for military purposes provided data that showed that the global mean temperature on Earth was indeed rising. Some people speculated that changes in the solar irradiance would also affect the temperature of Earth. Whatever the underlying reason , by the 1960s scientists estimated that the planet would warm by a few degrees over the coming century. Even though the physical feedback was poorly understood, scientists in the 1980s agreed that increasing the amount of carbon dioxide would increase the temperature of our planet. Data from ancient ice cores showed that a doubling of was correlated with a 3 degree rise in the global average temperature. Climate research intensified. With faster computers, it is now possible to carry out sophisticated simulations of the effect of rising carbon dioxide on the temperature of Earth.
::1896年,瑞典科学家Svante Arrhenius估计,人类燃烧煤炭会在大气中增加二氧化碳,造成少量变暖。这是一个好奇心,但很难想象当时的世界人口16亿将产生很大影响。到1930年代,为军事目的对气候的精确监测提供的数据表明,全球平均气温确实在上升。一些人推测,太阳辐照变化也会影响地球温度。不管根本原因为何,1960年代科学家估计地球将在下一个世纪中升温几度。尽管实际反馈不甚清楚,但1980年代科学家一致认为,增加二氧化碳将增加地球的温度。古代冰芯数据显示,二氧化碳的翻一番与全球平均温度上升3度有关。气候研究加强了。随着计算机的加速,现在有可能对二氧化碳上升对地球温度的影响进行精密的模拟。There are some effects of greenhouse gases outlined in the 2018 U.S. National Climate Report that are .
::2018年《美国国家气候报告》概述了温室气体的某些影响。-
The concentration of carbon dioxide (CO
2
) has increased from pre-industrial levels to 391 ppm in 2012 and is now rising at a rate of 1.8 ppm per year.
::二氧化碳(CO2)的浓度从工业化前的水平提高到2012年的391ppm,目前以每年1.8ppm的速度上升。 -
The present level of CO
2
is higher now than at any time in the last 15 million years. This information comes from paleoclimatic and geological evidence.
::目前的二氧化碳水平现在高于过去1 500万年的任何时候,这一信息来自古气候和地质证据。 -
Global mean temperature is about 1 degree C above pre-industrial levels and increasing.
::全球平均气温比工业化前水平高出约1摄氏度,而且正在上升。 -
The oceans have also been warming; 90% of the excess heat from increased greenhouse gases is stored in the oceans.
::海洋也在变暖;增加的温室气体产生的超热量90%储存在海洋中。 -
The loss of sea ice has tripled in the past 20 years.
::海冰的丧失在过去20年中增加了两倍。 -
Sea levels have
risen
by about 20 centimeters around the world and are now increasing at a rate of about 3 cm per decade. Melting from the continents of Greenland and Antarctica could add another 15 cm by the end of the 21st century.
::全世界海平面已经上升了约20厘米,现在以每十年约3厘米的速度上升。 格陵兰和南极大陆的融化可以在21世纪末再增加15厘米。 -
There has been a tenfold increase in extreme heat waves since the 1950s.
::自1950年代以来,极端热浪增加了十倍。
The consequence of 2-4 degrees of warming
::2至4度升温的后果Projecting the risks forward in time, every degree of warming exacerbates the stress on our planet and on civilization. The greatest warming occurs over land, bringing extreme heat waves, widespread drought, and increasing fires and deforestation. The resulting large-scale displacement of populations threatens security and economic systems. The higher temperatures and flooding of low-lying delta areas reduce crop yields and increase malnutrition and disease. Increasing carbon dioxide results in acidification that threatens marine life and ecosystems. A large-scale loss of biodiversity is already occurring with the loss of ecosystems. T he predictions are unacceptably dire if the global temperature increases by four degrees Celsius, as predicted for 2100 if we continue business as usual. Despite decades of warnings by climate scientists, we continue to miss our targets for reducing the use of the fossil fuels that are directly responsible for increasing greenhouse gases (carbon dioxide and methane).
::随着时间推移,各种程度的变暖都会加剧我们地球和文明的压力; 土地的变暖最为严重,带来极端热浪、大面积干旱以及越来越多的火灾和森林砍伐; 由此造成的人口大规模流离失所威胁到安全和经济体系; 低洼三角洲地区的气温升高和洪水减少作物产量,增加营养不良和疾病; 二氧化碳增加导致酸化,威胁海洋生命和生态系统; 生物多样性的大规模丧失已经随着生态系统的丧失而发生; 如果全球气温上升4摄氏度,如2100年预测的那样,如果我们继续照常运作,那么预测将是令人无法接受的可怕; 尽管气候科学家数十年警告,我们仍然未能实现减少使用化石燃料的目标,而化石燃料是增加温室气体(二氧化碳和甲烷)的直接原因。The data are unequivocal. We know what to do to mitigate climate change. But, this is a problem that we have to solve together. Will humanity answer this call to action?
::数据是明确的。 我们知道如何减缓气候变化。但是,这是一个我们必须共同解决的问题。 人类会响应这个行动呼吁吗? -
The concentration of carbon dioxide (CO
2
) has increased from pre-industrial levels to 391 ppm in 2012 and is now rising at a rate of 1.8 ppm per year.
