但危险的气候变化也可以很主观。
But dangerous climate change can be subjective.
试想一个极端天气事件，发生在世界的某个地方。
So if we think about an extreme weather event that might happen in some part of the world, and if that happens in a part of the world where there is good infrastructure, where there are people that are well-insured and so on, then that impact can be disruptive.
如果这个地方有着良好的基础设施，当地的人们都有着很好的保障等等，那这影响可能会是破坏性的。
It can cause upset, it could cause cost.
它可能会产生不必要的麻烦和经济损失，甚至可能会导致一些人死亡。
It could even cause some deaths.
但是如果同样的天气事件发生在世界上的某地，那里的基础设施很糟糕，或者人民的生命财产没有很好的保障，或者他们没有很好的社会支持网络，那同样的气候变化可能会带来毁灭性的影响。
But if that exact same weather event happens in a part of the world where there is poor infrastructure, or where people are not well-insured, or they're not having good support networks, then that same climate change impact could be devastating.
它可能会导致大量人流离失所，也可能会导致大量人员的死亡。
It could cause a significant loss of home, but it could also cause significant amounts of death.
现在让我们暂停并思考一下这个4℃的全球平均升温。
Now, let's just pause for a moment and think about this four-degree global average temperature.
地球上大部分地区是海洋。
Most of our planet is actually made up of the sea.
因为海洋比陆地有更大的热惯性，所以陆地上的平均温度会比海上的平均温度高。
Now, because the sea has a greater thermal inertia than the land, the average temperatures over land are actually going to be higher than they are over the sea.
还有就是我们作为人类不会体验到全球的平均温度。
The second thing is that we as human beings don't experience global average temperatures.
我们会体验到热天，冷天，雨天，特别是如果你和我一样住在曼彻斯特。
We experience hot days, cold days, rainy days, especially if you live in Manchester like me.
想象一下你身处一个城市中心。
So now put yourself in a city center.
在世界的某个地方：孟买，北京，纽约，伦敦。
Imagine somewhere in the world: Mumbai, Beijing, New York, London.
这是你经历过的最热的一天。
It's the hottest day that you've ever experienced.
火辣辣的太阳直射下来，混凝土和玻璃建筑环绕着你。
There's sun beating down, there's concrete and glass all around you.
想象在同样的一天——但是要比当天的热浪高出6，8，甚至10-12℃。
Now imagine that same day — but it's six, eight, maybe 10 to 12 degrees warmer on that day during that heat wave.
这就是我们即将要经历的全球平均升温4℃的情景。
That's the kind of thing we're going to experience under a four-degree global average temperature scenario.
这些极端气候带来的问题不仅仅是极端的温度，还有极端的风暴以及其他气候影响，而我们建造的基础设施还并不能承受这些极端事件。
And the problem with these extremes, and not just the temperature extremes, but also the extremes in terms of storms and other climate impacts, is our infrastructure is just not set up to deal with these sorts of events.
我们的道路和铁路网络被设计成只在一定程度的影响下才能经久耐用，世界各地都是如此。
So our roads and our rail networks have been designed to last for a long time and withstand only certain amounts of impacts in different parts of the world.
而这将面临极度的挑战。
And this is going to be extremely challenged.
我们的发电站本来是靠水来冷却到一个特定的温度，来保持设备的有效性和弹性。
Our power stations are expected to be cooled by water to a certain temperature to remain effective and resilient.
我们的建筑是被设计成在一定的温度范围内才能使人感到舒适。
And our buildings are designed to be comfortable within a particular temperature range.
而这些都将在4℃升温的情景下面临极大的挑战。
And this is all going to be significantly challenged under a four-degree-type scenario.
而我们的基础设施还无法应对这些挑战。
Our infrastructure has not been designed to cope with this.