"Humans are dominant cause of changes in the climate system": IPCC scientists in Climate Week NYC livestream

Clare Saxon Ghauri
27 September 2013

NEW YORK: Today IPCC climate scientists spoke live to an audience at Climate Week NYC, hours after releasing the IPCC AR5 report, which says humans are to blame for climate change.

The Intergovernmental Panel on Climate Change (IPCC) released the first part of its Fifth Assessment Report (AR5) on the 'Physical Science Basis' this morning, which sets the benchmark in the world’s understanding of the causes, impacts and potential solutions to climate change.

Dr Dennis Hartmann, professor of Atmospheric Science, University of Washington, Nathan Bindoff, Professor of Physical Oceanography and Climate Change and Ocean Processes program leader, University of Tasmania, and Dr Jochem Marotzke, Director, Max Planck Institute for Meteorology and vice chair of World Climate Research Programme, joined the event in Manhattan by video link from Stockholm, from where they had finished writing and released the IPCC AR5 report to the world hours before.

Dr Dennis Hartmann began the briefing by summarizing the overall statement of the AR5. He said: “Observationally, the AR5 is the same as AR4, in that global warming is unequivocal, based on many lines of evidence. A highlight from the report includes global estimates of anomalies of surface temperature in the atmosphere over the ocean which shows each decade is warmer than the decades before, measurements of which go back to 1850. The past 30 year period is warmer than any that we have experienced in the last 1400 years.”

Dr Hartmann explained how scientists have used natural recording systems such as measuring ice sheets, warming in the troposphere and temperature surface of the ocean. He shared how in the AR5 there is new evidence of ice sheet decline, with Greenland losing ice at a rate much faster than any other decade, as well as more evidence the sea level is rising. He said: “Sea level rise will have a huge impact on many people. It has been increasing at a more rapid rate that recent years, greater than any in the last 2 millenniums. Between 1901 and 2010 sea level rise was two tenths of meter.”

He added: “We can also measure with great precision greenhouse gases in the atmosphere like CO2, NO2 and methane. CO2 is up 40% more than in the pre-Industrial era. […] Data from CO2 in ice cores shows the concentration in the atmosphere is higher than it ever has been in the last 8,000 years. This is statistically significant.”

Nathan Bindoff, Professor of Physical Oceanography and Climate Change and Ocean Processes program leader, University of Tasmania spoke next on attributes to the warming. He said: “There are a few aspects that don’t allow us to say 100%, but what we can say is that the signal is more than 95% that man is the cause of global warming. There is very strong evidence that man is to blame for warming.” Explaining the AR5’s ‘clearer picture’ on the contributions of GHG gases on warming, he stated: “Humans are the predominant cause of changes in the climate system.”

Dr Jochem Marotzke, Director, Max Planck Institute for Meteorology and vice chair of World Climate Research Programme addressed the recent media dialogue around ‘current climate cooling and slowdowns’. He concluded: “Surface warming slowdown doesn't mean we're not in a warming world.”

During a panel Q&A which followed the video briefing, Dr Hartmann noted one of the key differences between the AR4 and AR5 reports: “We have moved from whether it is warming or not, to a question of how much it is has warmed.”

In a message to the IPCC conference in Stockholm earlier in the morning, UN Secretary General Ban Ki-Moon used the new results to call for urgent action from the world's business and government leaders. He said: "This new report will be essential for governments as they work to finalize an ambitious legal agreement on climate change in 2015. To add momentum to this process, I will convene a climate summit in September 2014 at the highest level. We need to seize the opportunities of a low carbon future. The heat is on. Now we must act."

The event, which was held at the New York Academy of Sciences, was part of the week-long summit Climate Week NYC, hosted by The Climate Group.

The Climate Group published a five-part briefing series covering the basics of climate science, ahead of the broadcast. Read them here.

Watch a video of the livestream

Related news:

“This is no longer about the science”: Entrepreneurs, policymakers, industry leaders agree it's time to act on climate, days before IPCC release

Mayor Bloomberg announces NYC has cleanest air quality in over 50 Years

One year on from Sandy, building resiliency to extreme weather across the US is still a matter of urgency

By Clare Saxon

Facebook icon
Twitter icon
LinkedIn icon
e-mail icon
Google icon