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One week after the record deluge in Texas, the biggest hurricane ever measured in the mid-Atlantic is tearing through the Caribbean.

For many scientists they are a worrying sign of a “new normal” in which extreme weather events become more intense as a result of manmade climate change. Rather than expressing astonishment, they say policymakers need to strengthen long-term countermeasures and act more effectively on reducing carbon emissions.

Following Harvey, which was a category four hurricane at its peak, a second major storm of this size in one season would be unprecedented, according to Weather Underground.

But historically unusual weather is no longer freakish. The floods that hit Houston last week were described as a once-in-500-years event because records suggested there was only a 0.2% chance of such heavy rainfall. However, precedent is an increasingly unreliable guide in a changing climate. In the past three years, Texas has been hit by three 100- to 500-year events, according to local media.