树木年轮的碳同位素和冰核中钚同位素的检测都显示出在上述阶段的大多数时间内太阳辐射能量出现下降。
Isotopes of carbon in tree rings and beryllium in ice cores show a drop-off in solar radiation during much of the period.
这种矩形机器人，看上去有点像缩小版的太阳能汽车。 它装备着高分辨率的摄像机和传感器，能探测到长的过分高大的树木。
The rectangular robot--looking a bit like a scaled down version of a solar car--is equipped with a high-definition camera and sensors that can detect overgrown trees.
虽然太阳活动降低了，但是我们燃烧化石燃料和砍伐树木引起了CO2的快速升高。
This small weakening of the sun, however, has been outpaced by the rapid increase in CO2 levels from all our fossil fuel burning and tree-cutting.
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