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Climate literacy.

You’re at a dinner party or other social event and someone asks what you do for a living. A feeling of dread washes over you. If the person you’re talking to identifies with the far right of the political spectrum or reads too much of the Murdoch press, then things are likely to get awkward. You cross your fingers, say that you work as a weather/climate scientist, and hope for the best.

 
I think we can all relate to this situation. We all work in our own niche area, but the reality is that weather/climate science has become highly politicised. Like it or not, there are times (like social occasions) when you will be called upon to comment on aspects of the broader discipline. In order to equip you for these situations, this page provides an ever evolving collection of the latest, general interest research findings. It does not cover climate science basics (I’m assuming that you were paying attention as an undergraduate), nor is it a guide to explaining weather/climate science to lay people. Instead, it is simply a list of new and interesting research findings that are highly relevant to the public discourse. It is my hope that you will whip them out at social events and wow people with the depth and breadth of your understanding (i.e. your climate literacy). If you do find yourself faced with the task of explaining climate change to a general audience in a public forum, you might find the recording and slides from my presentation at Nerd Nite Melbourne useful.

If you think of any worthy additions to the list, please feel free to post a comment below.

The Earth’s energy imbalance
Global warming hiatus periods
How long have we known that climate change is happening?
Extreme weather and climate change
Geo-engineering

 
The Earth’s energy imbalance

Due to the Earth’s large thermal inertia, increasing greenhouse gas concentrations have led to a radiation imbalance at the top of the atmosphere. Observational (Trenberth et al 2009; Murphy et al 2009) and model (Hansen et al 2012) estimates place the current imbalance at about 0.6 W m-2 (i.e. more energy is coming in than going out). The planet will continue to warm until the radiation balance is restored.

In order to stabilise the Earth’s climate (i.e. to stop global warming in its tracks), atmospheric carbon dioxide concentrations would need to be reduced to about 350ppm (Hansen et al 2012). This finding was the basis for establishment of the climate action group known as 350.org.

‘Live’ carbon dioxide readings can be easily accessed from Cape Grim in Australia and Mauna Loa in Hawaii. It is sobering to note that we are approaching 400ppm, at a rate over 2 ppm per year. In fact, after a brief slow down due to the global financial crisis, 2012 saw the second largest single year increase in atmospheric carbon dioxide on record (2.67 ppm; read here).

 
Global warming hiatus periods

It is often noted that the rate of increase in global average surface temperature has slowed over the past decade or so. In fact, inspection of the global surface temperature timeseries for the past century reveals a series of ‘step’ increases in temperature, as opposed to a constant linear rise. The plateaus (or step landings) in this timeseries are commonly referred to as global warming hiatus periods. However, given the known radiation imbalance, the excess energy that the Earth is accumulating during these periods has to go somewhere (i.e. if not into warming the atmosphere, then either into melting ice or warming the ocean). Recent model (Meehl et al 2011) and reanalysis (Balmaseda et al 2013) studies suggest that during these periods, the excess energy is predominately taken up by the deep ocean.

The IPCC Fifth Assessment Report discusses the most recent hiatus in some detail. In addition to increased deep ocean heat uptake, they also identify a number of other natural forcings (e.g. higher than normal volcanic activity and a solar minimum) that have acted to counteract the warming that would otherwise have occurred.

 
How long have we known that climate change is happening?

While the existence of the greenhouse effect and the role of carbon dioxide in regulating the climate were first recognised during the 1800s (see Wikipedia discussion), the first documented evidence that the planet had recently warmed didn’t appear until 1938. In an article published by the Quarterly Journal of the Royal Meteorological Society, an amateur climatologist by the name of Guy Stewart Callendar described his analysis of temperature readings from 147 weather stations scattered across the globe (but excluding the polar regions). By averaging them together to produce an estimate of the global average temperature, he estimated that the planet had warmed by about 0.3°C over the previous 50 years. Significantly, Callendar also suggested that the production of carbon dioxide by the combustion of fossil fuels was responsible for a large part of this warming.

The role of carbon dioxide was debated in the decades following, partly because the warming plateaued until the mid 1970s (probably due to aerosol emissions). However, by the 1980s the climate science community was very confident that anthropogenic emissions had the potential to dramatically alter the Earth’s climate. James Hansen testified to congress about the dangers of climate change in 1988, and in the same year the Intergovernmental Panel on Climate Change was established. The rest, as they say, is history.

To celebrate the 75 year anniversary of Callendar’s work, a great paper and blog post were published.

 
Extreme weather and climate change

If you often get a little tongue tied when trying to explain the link between climate change and extreme weather events, then Trenberth (2012) is a must read. Among many other insightful comments, Trenberth notes that the answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change, because the environment in which they occur is warmer and moister than it used to be.

 
Geo-engineering

There are essentially three options available for reducing the risks associated with climate change: (1) reduce emissions (mitigation), (2) adapt to the changing climate, (3) deliberately manipulate the climate system in order to counteract the effect of increasing greenhouse gas emissions (geo-engineering). While no large-scale geo-engineering projects have been undertaken to date, there are plenty of ideas floating around. In fact, the level of discussion around geoengineering has been sufficiently high to prompt both the American Geophysical Union and American Meteorological Society to adopt a formal position statement on the issue.

Broadly speaking, geoengineering ideas can be placed into one of two categories. The first, known as carbon dioxide removal techniques, includes ideas like planting trees, carbon sequestration (i.e. capturing emissions and storing them underground) and ocean nourishment (including iron fertilisation). The second, known as solar radiation management techniques, includes a range of surface based (e.g. white roofs on buildings), troposphere based (e.g. modify cloud properties), upper atmosphere based (e.g. pump reflective aerosols into the upper atmosphere) and space based (e.g. obstructing solar radiation with space-based mirrors) proposals.

It is fair to say that there are serious concerns associated with pretty much all of these ideas (perhaps with the exception of planting trees). These range from concerns about specific methods (e.g. ocean nourishment could severely alter marine environments) to more general ethical, legal, economic and political concerns. The solar radiation management techniques are particularly concerning, because even if we were successful in reducing the global mean temperature back to a pre-industrial value, we wouldn’t ‘get back’ the climate we once had. For instance, the GeoMIP project and other similar modelling studies (e.g. Bony et al 2013) have found that the global hydrological cycle, which determines the location and intensity of global rainfall, differs substantially from pre-industrial times under simulated radiation management scenarios.

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4 Comments

Leave a Comment
  1. Nicholas Tyrrell / Apr 4 2013 13:48

    How about Compo et al’s new paper in GRL: ‘Independent confirmation of global land warming without the use of station temperatures’. Here’s the link http://onlinelibrary.wiley.com/doi/10.1002/grl.50425/abstract

  2. Craig Arthur / Apr 4 2013 19:18

    I regularly read Roger Pielke Jr.’s blog (http://rogerpielkejr.blogspot.com.au/) on the mix of science and policy. Roger also has a big interest in natural disasters – which is how most people feel the impacts of climate change – and he provides some really good insight into this aspect of climate science. Not so much a single paper, but certainly it’s a great way to keep up to date with the latest research.

  3. Damien Irving / Sep 1 2014 13:43

    If you are looking for a similar ‘climate literacy’ page for lay people, NOAA have produced a great resource… http://cpo.noaa.gov/OutreachandEducation/ClimateLiteracy.aspx

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