The International Monetary Fund's World Economic Outlook update predicted that the global economy would grow 0.1% less than anticipated.
The global economy is now forecast to grown by 3.5% in 2013 and 4.1% in 2014.
Much of the reduction stemmed from a weaker outlook for the eurozone.
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Temperatures will reach around 28 Celsius (82F) at their highest.
A minute's silence will be observed at 11am on Thursday in remembrance of those who lost their lives in the Manchester Arena attack.
New research has found those who consumed two cups had a 35% reduced risk, and for those who drank five cups, the risk halved.