NASA has published data showing that 2009 was the second warmest year on record, offering a serious challenge to a popular alternative theory to man-made climate change. That theory blames global warming on increases in energy coming from the sun, but in 2009 the sun was the least active it has been for 100 years. The Skeptical Science blog does admit that this comparison, which it made earlier today, is “cheeky”, as using only small numbers of measurements like this can be misleading. However, author John Cook points out this is just the latest in a string of evidence showing that there has been no correlation between solar activity and the Earth’s temperature since 1975.
Meanwhile, Richard Katz of Cambridge University and Grae Worster of Oxford University have suggested that a large piece of the Antarctic may already be sliding into the sea. They have modelled how Antarctic ice sheets move, focussing especially on the “grounding line”, an underwater junction where floating ice sheets anchor to the sea bed. As the ocean warms, the ice melts from below, meaning that the grounding line rises ever higher up the Antarctic land mass. “Do recent changes represent a mounting, catastrophic collapse associated with unstable retreat of grounding lines or, rather, a steady and controlled adjustment?” Katz and Worster ask. From the results of the model, they conclude that unstable grounding line retreat may already be ongoing on a body of ice known as the Pine Island glacier. According to New Scientist, this would mean that the Pine Island glacier is now unavoidably set to lose half of its ice, creating a 24 cm sea rise over the next 100 years.
Few people reading this blog will live to see the full impact of that, but our actions today will be crucial in determining what the world does look like in the 22nd century. That’s the key message of a paper published online this week by a collaboration between scientists in the US, Austria, and the Netherlands. They modelled how CO2 production must be reduced to keep global temperature rises below 2°C – a limit acknowledged in the Copenhagen accord – by 2100. Among a wide range of outcomes they model, to have a 50:50 chance of limiting warming below 2°C in 2100, emissions in 2050 would have to be 72% of what they were in 2000.
The good news this week was that investors representing $13 trillion of assets called on the US and other nations to move quickly on meeting such targets. 450 US, European, and Australian signatories released a statement at the Investor Summit on Climate Risk, at the United Nations on Thursday. “We cannot wait for a global treaty,” the statement said, calling for rapid action on emission limits, energy efficiency and renewable energy. Let’s hope that their own actions, and those of the companies invest in, are also in line with what they demand from the authorities.