尸体上满是刺伤。Beside the body lay a bloody knife,画在墙上，a message: I,杀人犯，用刀杀人。Below the message were the name and address of the killer,连同他的纳税申报表，several photographs,and details on how to follow him on social media.
The detective frowned.This would be a tough case to crack.He turned to his partner."怎样，"他说，"can we be sure it's not the Sun?""
Sometimes I feel like climate scientists live in an alternate-universe Law and Order,where the detectives are less attractive and every episode begins with an argument over whether objective reality exists.Imagine how boring crime dramas would be if the police were forced to spend the first 45 minutes explaining that yes,they are aware that people die of natural causes all the time.
In reality,事实很清楚：我们的世界正在改变，and there are fingerprints all over the scene.We've collected plenty of evidence.我们知道，beyond any reasonable doubt,这是谁干的。
但是气候一直在变化，say people to the scientists whofigured that out.这是真的：很多东西都会影响地球的温度。一次大的火山喷发会把大量的气体和灰尘喷洒到大气中，从而阻挡太阳。Natural variations in the Sun's brightness or the Earth's orbit can make it warmer or cooler.We can measure these things—if the Sun suddenly got much brighter,I'm pretty sure someone at NASA would notice.我们可以利用我们对地球系统如何工作的理解来了解它们可能对气候的影响。
A few years ago,we worked with Blacki Li and Eric Roston of Bloomberg News to explain why we're so sure humans are causing global warming.利用复杂的地球系统计算机模型，我们计算了每个单独因素在隔离中的影响。The他们制作的图案很精彩，当它再次在Twitter上流行时，这是一个好迹象，一些著名的政治家说了一些关于气候变化的愚蠢的话。这是我见过的关于谁导致气温升高的最清楚的解释。
The data we used for this project extended only to 2005.But warming has continued through the 21ST世纪。2015年是有记录以来最热的一年……直到2016年。Last year was the hottest year ever measured to not have an added boost from a natural El Niño event.Greenhouse gas emissions have continued to increase,and they continue to be the prime suspect behind global warming.
Climate,当然，is more than just the average temperature.We've seen human fingerprints all over the planet.海洋正在变暖，变得更酸，大气中含有更多的水蒸气，热浪越来越频繁和强烈。The science of climate change detection and attribution—climate detective work—has advanced to the point that we can now confidently blame human activities for some individual extreme events.
科学家们在这里总是可能犯了严重的错误。但是如果你不相信人们影响了气候，对于我们所看到的变化，您需要一个连贯的替代解释。此外，你需要解释为什么二氧化碳不能像我们认为的那样起作用。It could be that we've all been wrong about the greenhouse effect this whole time.But overturning that understanding would take a radical paradigm shift that would call into question much of what we know about physics and chemistry.It's possible,但这是一个很高的要求。
We have the evidence,and we've done the forensics.The culprit has been identified beyond a reasonable doubt.It doesn't strike me as very useful to argue that because people die of natural causes all the time,murder can't possibly exist.这是电视节目的糟糕前提，一种奇怪的思考世界的方式。But it's never enough to collect evidence—we have to argue our case and convince a jury.那陪审团呢？是我们。
But with climate change,我们不仅仅是法官和陪审团，我们是受害者，and the culprits too.We can reduce our sentence through good behavior—radically slashing greenhouse gas emissions and decarbonizing our economy.但我们不能假装没有犯罪。对我们的指控太清楚了。