The landmark IPCC report is out. Here’s the punchline: “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”
Confidence in man’s role in climate warming has increased incrementally since IPCC conducted its first assessment in 1990 – that is important to appreciate.
But there is much more to understand about this report, and what it means. Here are five prevailing themes and intelligent voices speaking to them, drawn from an array of press coverage:
1) Man’s role in global warming is rock solid, and natural variability’s role is close to nil.
“Natural internal variability and natural external forcings (eg the sun) have contributed virtually nothing to the warming since 1950”
Stefan Rahmstorf, climate scientist
“[C]lose to 100% of the observed warming is due to humans.”
2) This report is extremely authoritative
“It is probably the largest, most comprehensive scientific assessment in history. Not just of climate change, but of any scientific subject”
“In arriving at its conclusions, the group combed through 9,200 scientific publications, two-thirds of which were published after 2007, and considered the input from nearly 55,000 comments drawn from 1,089 reviewers from 52 countries. A majority of the scientists involved in the latest report were new to the IPCC process.”
– Andrew Freedman, science writer, Climate Central
“”This isn’t a run of the mill report to be dumped in a filing cabinet. This isn’t a political document produced by politicians… It’s science.”
3) Warming has slowed in the last 15 years, but not stopped. (If the slow down in warming persists, it would suggest a problem with the models.)
“The global average surface temperature trend of late is like a speed bump, and we would expect the rate of temperature increase to speed up again just as most drivers do after clearing the speed bump.”
“The current pause is consistent with numerous prior pauses. When walking up stairs in a tall building, it is a mistake to interpret a landing as the end of the climb”
“Certainly if we experience [a slowdown] for the next 20 years, we cannot be confident in the models.”
4) There has been no pause in ocean warming.
“The heat content of the oceans is growing and growing. That means that the greenhouse effect has not taken a pause and the cold sun is not noticeably slowing global warming.”
5) The warming poses real risks. We hold the key to reducing them.
“I was struck by how the IPCC report reads like lab results from a sick hospital patient. The natural systems that civilization depends upon to thrive have been profoundly disturbed, and the forecast for the future reads like a medical diagnosis for an overweight smoker with a heart condition: unless the patient makes major lifestyle changes, the illness will grow far worse…”
“For decades to come, we’re locked into generally rising temperatures, with shorter-term temperature shifts* — up or down — shaped most by natural variability in the system (as with the recent plateau in temperatures). But humanity, by acting in ways that blunt emissions of greenhouse gases, can significantly affect the rate of warming and other related conditions from mid century onward.”
“…the response to global warming is more about ethics and economics than data.”
““Humankind has a choice on which scenario we will face in the coming 100 years or so. It depends crucially on how much carbon dioxide will be emitted in the future.”
– Thomas Stocker