Insights

Exploring the link between extreme weather and climate change.

As flood warnings remain in place across much of Yorkshire with more heavy rain expected in the coming days, we’re faced yet again with the devastating impact that extreme weather events can have on our society.

For those affected by the floods, getting back to normality will be the number one priority. However, for those of us involved in the planning, design and construction of the built environment, there’s a different focus.

Is there a link between climate change and extreme weather events?

In short, yes.

Although it’s not possible to attribute individual weather events to climate change, there has long been a consensus that warming the planet will increase the frequency and intensity of extreme weather events. Physically, this is analogous to a pan of water being heated over the hob – convection currents increase as the bottom of the pan gets warmer and eventually the still water is brought to a rolling boil.

The 2012 IPCC special report: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, predicted that increases in temperature extremes, sea levels, frequency of heavy precipitation events, tropical cyclone maximum wind speeds and drought intensities are likely during this century.

The report also highlights that weather observations from the 1950s demonstrate that changes in some extremes have already occurred, and that some extremes are likely to have changed as a results of human activity.

How could the weather change in the UK?

The weather in the UK may already to be getting more extreme, as the headlines from the Met Office’s 2018 State of the UK Climate report appear to demonstrate:

– Average sea levels around the UK in 2018 were the highest on record.
– 10 named storms hit the UK in 2018.
– 6 of the 10 wettest years on record all occurred since 1998.
– The top 10 warmest years on record all occurred since 2002.
– Over the last decade (2008 – 2018), summers were 13% wetter and winters were 12% wetter.

This broadly re-affirms the previous 2009 climate projections (UKCP09). However, advances in convection modelling techniques now give a clearer picture of how convective weather events might develop in a warmer climate. It suggest that although summers are expected to get drier overall, summer showers will become more intense (making surface water flooding more frequent and severe). Significant increases in hourly precipitation events are also expected, with the likelihood of rainfall events, which typically occur once every two years, increasing by 25%.

How can we prepare for extreme weather events?

In July this year, the Committee on Climate Change issued a report to parliament on the progress in preparing for climate change. Its conclusions were stark. We are now seeing the substantial impacts of a global temperature rise of 1°C, however England is not prepared for impacts of a 2°C increase, let alone a 4°C, which may be likely given the current global trajectory.

Industry guidance has been strong in this area for a number of years, and although climate models and predictions may change, the principles of preparing for severe weather remain the same.

The 2005 report: Adapting to Climate Change: a Checklist for Development, by the Three Regions Climate Change Group contains practical advice on creating resilient buildings and covers location, site layout, building design, structure, envelope and materials, ventilation and cooling, drainage, water, outdoor spaces and connectivity.

The need to provide buildings that are capable of meeting the demands of the future is also recognised by the BRE. The BREEAM New Construction 2018 environmental assessment method identifies a group of credits that are specifically focused on this area. The credits are designed to create developments that are less prone to flooding, capable of regulating internal temperatures in future climates without the need for mechanical cooling, more resilient to the effects of weather degradation, and use energy and water efficiently to meet the needs of their occupants. If targeted together, this provides developers with an opportunity to deliver robust buildings that stand the test of time and might even contribute an additional 13% or so to the BREEAM score.