Established laws of physics used to make climate projections

PUBLISHED : Wednesday, 03 August, 2016, 4:20pm
UPDATED : Wednesday, 03 August, 2016, 9:25pm

I refer to the letter by G. Bailey (“Observatory’s objectivity questionable”, July 21).

In the second edition of “Hong Kong in a Warming World” (, the Hong Kong Observatory has updated the climate projections for the globe and Hong Kong, taking into consideration the emission reduction pledges made at the Paris climate summit (COP21) in late 2015.

While the COP21 pledges aim to steer the world away from the worst scenario, the projection results suggest that the world could still be heading towards a temperature rise of around three degrees Celsius (relative to pre-industrial levels), and more mitigation efforts in reducing carbon emission are required to achieve the COP21 target of keeping global temperature rises below two degrees.

Adaptation efforts are also needed to make our city more resilient to climate change effects including a higher chance of extreme weather.

As the world is finally taking positive steps in the right direction, your correspondent has refused to acknowledge the reality of the situation and continues to make use of your newspaper to spread sceptical and denial views that are counterproductive and scientifically unfounded.

The Hong Kong Observatory has tried its best to respond time and again, and I am not going to take up more of your columns reprising all the arguments here.

While G. Bailey can pick and choose what to believe, the Observatory is a government department with a purview on climate change science and related issues. It has a duty to inform and educate the general public based on the best information and evidence available, such as the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change that represents the consensus view of climate scientists.

Climate projections are generally based on objective numerical modelling techniques in accordance with well-established laws of physics.

Of course, projection so far into the future always contains an element of uncertainty, but the driving force of nature behind such laws would lead to trends that are inevitable if we continue regardless with unchecked greenhouse gas emissions.

Lee Sai-ming (senior scientific officer), Hong Kong Observatory