Tens of thousands of people from all over the world joined one of the biggest turnouts of climate change activists yesterday, telling world leaders gathering for a summit in Paris that there is "no planet B" to which humanity can flee. In the French capital, where demonstrations were banned after attacks by Islamic State terrorists killed 130 people on November 13, activists laid out more than 20000 pairs of shoes in the Place de la Republique to symbolise absent marchers.Among the high heels and sandals was a pair of plain black shoes sent by Pope Francis, who has been a vocal advocate for action to prevent climate change, and jogging shoes sent by UN secretary-general Ban Ki-moon.One activist, dressed as an angel, with large wings, held a sign reading "coal kills".About 10000 people joined arms to form a human chain through Paris along the 3km route of the banned march, organisers said.More than 2000 events were held in cities such as London, Sao Paulo and New York, making it perhaps the biggest day of climate-change action in history - all on the eve of the Paris summit, which runs from today to December11 and will be attended by about 150 heads of stateIn Sydney about 45000 people are estimated to have marched through the central business district towards the Opera House.Protesters held placards reading: "There is no Planet B," and "Say no to burning national forests for electricity".Organisers hope the summit will produce the first legally binding agreement to commit rich and developing nations to continue curbing emissions of greenhouse gases beyond 2020. ..