the job of the barrier is to keep london safe from flooding, and right now, it's coming up to high tide, and the great steel gates are holding back a phenomenal volume of sea water that would otherwise enter the city and potentially cause disaster, which is why climate change matters so much here. they're constantly watching the projections for how much the sea is going to rise. it's also why we'll probably need a bigger barrier by 2070. and this was what first hit me about climate change. while some countries can afford gleaming steel structures like this, most others can't.