Australian Broadcasting Corporation: Researchers in Queensland’s far north are still unclear about the effects of carbon dioxide on tropical rainforests. James Cook University’s Professor William Laurance will hold a lecture in Cairns this afternoon to discuss climate change in the far north. Professor Laurance says scientists are divided over whether the increase of carbon dioxide in the atmosphere is harming or helping rainforest trees. “Some people think the increasing levels of CO2 are going to force forests to grow more…