Archives for 2016

My free online class on Coursera.org entitled Global Warming I: The Science and Modeling of Climate Change has already served 45,000 people (started, not finished) in the four times that it’s run. Now it’s set up in a new format, called “on demand mode”, which allows people to start, progress, and finish on their own calendars. This would be an advantage if a teacher wanted to use the material to supplement a class; a new cohort of learners is launched every month, so the next class start date is never more than a month away.

A new, supplemental class to the first one has been added and will come online on Monday, called Global Warming II: Create Your Own Models in Python or Fortran. This takes advantage of new code-grading machinery at Coursera to automatically run your code through its paces. There is also a peer code-review step, where you will get feedback on your commenting and variable-naming skills, and provide feedback to others. The class gives detailed instructions to create simple models of: time evolution of global temperature, the ice albedo feedback drop into snowball Earth, an ice sheet, and a shallow-water circulation model. The class is intended for people who are new to programming, or new to Python, or wish to enhance their understanding and appreciation of some cool science of Earth’s climate system.

The classes are supported by the same interactive on-line interactive climate system models as before, at http://climatemodels.uchicago.edu/, with some new additions, both of which generate animations of their time-dependent solutions.

One is a Hurricane simulator using a model from Kerry Emanuel, which can demonstrate the sensitivity of ocean temperature, ocean mixing, and atmospheric structure on hurricane evolution.

The other, the Permafrost model, is a simulation of a soil or sediment column in which ice and methane hydrate can form. The model shows how the brine salinity thermodynamically excludes methane hydrate from forming until you get to the base of the permafrost zone, and also how long it takes to warm a soil column by warming the surface. This model shows why I do not believe in an imminent methane climate catastrophe from Arctic Ocean methane hydrates.

With the official numbers now in 2015 is, by a substantial margin, the new record-holder, the warmest year in recorded history for both the globe and the Northern Hemisphere. The title was sadly short-lived for previous record-holder 2014. And 2016 could be yet warmer if the current global warmth persists through the year.

One might well wonder: just how likely is it that we would be seeing these sort of streaks of record-breaking temperatures if not for human-caused warming of the planet?

Precisely that question was posed by several media organizations a year ago, in the wake of the then-record 2014 temperatures. Various press accounts reported odds anywhere from 1-in-27 million to 1-in-650 million that the observed run of global temperature records (9 of the 10 warmest years and 13 of the 15 warmest years each having had occurred since 2000) might have resulted from chance alone, i.e. without any assistance from human-caused global warming.

My colleagues and I suspected the odds quoted were way too slim. The problem is that each year was treated as though it were statistically independent of neighboring years (i.e. that each year is uncorrelated with the year before it or after it), but that’s just not true. Temperatures don’t vary erratically from one year to the next. Natural variations in temperature wax and wane over a period of several years. [Read more…] about How Likely Is The Observed Recent Warmth?