In May 2013, it was reported that readings for CO 2 taken at the world's primary benchmark site in Mauna Loa surpassed 400 ppm . According to professor Brian Hoskins , this is likely the first time CO 2 levels have been this high for about million years.   Monthly global CO 2 concentrations exceeded 400 ppm in March 2015, probably for the first time in several million years.  On 12 November 2015, NASA scientists reported that human-made carbon dioxide continues to increase above levels not seen in hundreds of thousands of years; currently, about half of the carbon dioxide released from the burning of fossil fuels is not absorbed by vegetation and the oceans and remains in the atmosphere. 
However, it has long been argued that prices don’t truly reflect the full cost of things, so either the signal is incorrect, or comes too late. The price signal also implies the poorest often pay the heaviest costs. For example, commercially over-fishing a region may mean fish from that area becomes harder to catch and more expensive, possibly allowing that ecosystem time to recover (though that is not guaranteed, either). However, while commercial entities can exploit resources elsewhere, local fishermen will go out of business and the poorer will likely go hungry (as also detailed on this site’s section on biodiversity ). This then has an impact on various local social, political and economic issues.