by Professor Bruce Hewitson

“Among climate scientists, this is not a controversial topic. But among the general public, it IS controversial.”

Visual: Indicators of a warming world. Visual from

This comment at a recent public discussion forum captures the issue in a nugget – overwhelmingly the evidence s so strong that humans are seriously changing the planet, that its almost impossible to rationally deny human forced global change, if you honestly face the multiplicity of evidence.

So what has/is happening?  Fundamentally we are changing the energy state of our planet due to causing elevated greenhouse gas concentrations.  If you change the energy state, the behaviour of the system changes.  This change has multiple expressions, increased temperatures being the one most cited.  But included in the changes are things like increased intensity of weather events, ice sheet and glacier melt, sea level rise, elevated atmospheric humidity, ocean warming, seasonal shifts, etc.

The problem is, society and ecosystems are equilibrated to a historical range of variability.  Global change is shifting this “envelope” of natural variability so that systems are no longer in equilibrium.  That means we are pushing systems towards their thresholds of viability in their current state, and this requires adaptation.  For example, a city designs it’s storm water system to accommodate an expected range of rain intensity.  If intensity increases, at some point the storm water system is no longer adequate, and either there is substantial impact, or adaptation measures have to be urgently retrofitted.

One can consider any social, industrial or bio-physical system, and find their thresholds.  Some will be vulnerable to climate changes, some will not.  The key is to identify which thresholds are important, and how climate change relates to these.

Facing this challenge there are some who would prefer to ignore and/or deny the reality of change.  They may do so because they are misled, or ignorant of the facts, or selfishly placing their own comfort zone above the needs of society, or they may be driven by vested interests to maintain the status quo.  In the political arena, this hesitancy is also found (climate change is not a popular vote-winner!), and this is problematic as we desperately need strong leadership to address the challenges.

So how do we respond?  There is no single answer, but at a minimum we need to educate ourselves about the facts, we need to understand our individual responsibility in bringing about a shift in modes of consumption, and we need to build resilience into our lives and engage in adaptation to identified stress factors.  This is not a case of each for themselves, but a cooperative exploration of local and regional issues, and a participation in a societal shift.  We can leave it till later and put the burden on our children, or we can choose to engage now.

As a start on your exploration, here are a sample of references that I would trust.  Bear in mind the internet can be like a garbage pit … full of rubbish, nuggets of truth, and where not all that glitters is gold!

If you have the bandwidth, you may also find these videos a useful starting point: