The potential effect of climate change and global warming on gardening and
gardens
Information taken from:An on-line Future Learn course 2014 IPCC report RHS website
Lyn Beazley
Climate and weather
Climate looks at how the weather changes over a long period of time, typically around 30 years
Weather is the elements we see daily such as temperature, rain and wind.These can change hour by hour and day by day
The climate system, feedbacks, cycles and self-regulation
Climate can be conceptualised as a system.
It's a system that self-regulates thanks to a mixture of positive and negative feedback. They link together the different components of the climate system.
Past climate change
Earth has self-regulated for the past 4 ½ billion years by the process of chemical weathering.
Past climate change
Carbon dioxide and rainwater forms a weak acid, carbonic acid, that dissolves silicate rocks
The carbon in the form of bicarbonate ions washes into the ocean, where it is used by many organisms to form their shells, which are then deposited on the ocean bed to form carbonate rocks
So, carbon dioxide from the atmosphere is transferred through the hydrosphere (oceans) to be stored in the lithosphere (surface of the earth’s crust)
Recent past climate change
The last 2 million years is called the quaternary period which has seen some really big climate changes.
How is climate change affected by natural factors?
Over the last 2.6 million years, the climate has been affected by a range of types of forcing factors (eg a more active sun during the medieval period; global volcanic activity)
Evidence of changes found in tree rings and ice cores
Recent past climate changes
Predictable changes: Earth’s orbit round the sun.
Unpredictable changesSolar variability - variations in the amount of energy that the sun puts out. Global volcanic activity
Recent past climate changes
Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer. (Graph adapted from Mann et al., 2008.)
Temperatures continue to rise
YearGlobally averaged combined land and ocean surface
temperatures
Each of the past 3 decades has been successively warmer than the preceding decades since 1850
AR5 WGI SPM
Current situation
170 years of data shows:
• Significant temperature rise over 20th century up to the present day. Pattern for increasing ocean temperatures is similar.
• Since 1880, there's been a steady rise in sea levels. • Part of the world where temperature rises have
been their highest is the polar arctic region.
Oceans absorb most of the heat
– More than 90% of the energy accumulating in the climate system between 1971 and 2010 has accumulated in the ocean
– Land temperatures remain at historic highs while ocean temperatures continue to climb
AR5 SYR
Our changing carbon cycle
The graph shows recent monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii.
Future projections
• Climate projections are made with climate models, which, like weather forecast models, break up the world into a number of boxes.
• They try to simulate how the temperature,
humidity, and wind in the atmosphere, and how the temperature salinity and ocean currents in the ocean vary through time
Future projections
Climate models tested to see if they can reproduce the observed past.
They include aspects such as natural factors, eg sun’s output; volcanic activity
When the natural factors are added, it’s found that the models can reproduce aspects of the climate, but only until about 1970.
Future projections
But when the human factors are added to the calculations, particularly the increasing carbon dioxide that’s been associated with burning fossil fuels and deforestation, models reproduce the observed warming extremely well.
Future projections
Intergovernmental Panel on Climate Change (IPCC) has made quite definitive statements about the causes of global warming.
They are able to say that there is a 95% chance that the global warming we've seen today is due to man-made greenhouse gases, and that is despite the uncertainties we have in climate models and in observations.
How much more will earth warm?
Model simulations by the IPCC estimate that Earth will warm between two and six degrees Celsius over the next century, depending on how fast carbon dioxide emissions grow.
Scenarios that assume that people will burn more and more fossil fuel provide the estimates in the top end of the temperature range, while scenarios that assume that greenhouse gas emissions will grow slowly give lower temperature predictions.
How much more will earth warm?
The orange line provides an estimate of global temperatures if greenhouse gases stayed at year 2000 levels. (©2007 IPCC WG1 AR-4.)
Projected climate changesContinued emissions of greenhouse gases will cause further warming and changes in the climate system
Global mean sea level will continue to rise during the 21st century
It is very likely that the Arctic sea ice cover will continue to shrink and thin as global mean surface temperature rises
Oceans will continue to warm during the 21st century
AR5 WGI SPM
Future projections
IPCC’s full report can be found at:
• http://www.ipcc.ch/report/ar5/wg1/#.UpdejcQRB8E
Impacts on human systems
Human health and the built environment
• Urban heat islands• Heat wave• Body heat
Impacts – urban heat islands
Land surface temperatures in cities, particularly densely-developed cities, tend to be elevated in comparison to surrounding areas -- a phenomenon called an urban heat island. Credit: NASA
Impacts on human systems
• More links on urban heat islands http://www.nasa.gov/topics/earth/features/heat-island-sprawl.html
• http://earthobservatory.nasa.gov/IOTD/view.php?id=36227
Food security
Climate change and food security
40% of global agricultural land produces just four types of crops:• Rice• Wheat• Maize • Potatoes
Food security
Since 1960s Green Revolution
– Monocultures• fertilisers• herbicides• pesticides• fungicides• farm mechanisation
Food and plant security
Security of food supplies/plants at risk:water (excess or droughts)pests and diseases weeds fungi (moving over 7 kilometres per year towards the poles in a warming world)
Food security
Some UK figures for 2009:• we import 30% of our food• our food wastage was 4.1M tonnes of food
nationally • 60% of nitrates, 25% of phosphorus and 70%
of sediments polluting water bodies come from farms
Food security
The global food security programme
• http://www.foodsecurity.ac.uk/index.html
Mitigation points
More efficient use of energy
Greater use of low-carbon and no-carbon energy• Many of these technologies exist today
Improved carbon sinks• Reduced deforestation and improved forest management
and planting of new forests • Bio-energy with carbon capture and storage
Lifestyle and behavioural changes
Global weather predictions
More extreme weather events:
– More frequent wildfires– Longer periods of droughts– Increase in number, duration and intensity of
tropical storms (warm air holds more water)– Increase in ‘extreme’ weather events
Local predictions
• Floods• Droughts • Increased rain in winter/flash floods• Warmer, wetter winters (for each 1 degree C
rising of temperature = 100 miles move south. Current rise from 1880 is 0.85 degrees C)
• Longer, dryer summers (Spring now 11 days earlier compared to 30 years ago)
RHS advice
Might be opportunity to grow exotic fruits and sub-tropical plantsBUTIncreased winter rainfall will make it difficult for Mediterranean species which dislike water loggingSharp frosts still likely
RHS advice
• Warmer temperatures can bring new pests and diseases:
lily beetles, rosemary beetle, berberis sawfly, red spider mite, new vine weevil species• Fungal diseases thrive with wet winter
conditions
RHS advice
What are the endangered plants?
Those which require fertile, moisture-retentive soil, such as:
delphiniums and lupinsSpring displays of bulbs and tuberous
plants which will be susceptible to problems with wet winters
RHS advice
CO2 is processed by plants through photosynthesis.
With increased CO2 in the atmosphere, plants and especially trees can grow faster and stronger
Planning for the future
• Plant for the future, using trees, shrubs and hedges that are drought-tolerant
• Green spaces will be vital to counteract the urban heat island effect
• Plant windbreaks to protect gardens from stormier weather
Planning for the future
• Prepare soil thoroughly to maximise drainage, adding organic matter, gravel or grit
• If planning for a new garden, allow for irrigation
• Allow for plants that will offer shade in the summer
Planning for the future
Set up water butts to conserve water
• Drinking water will be in increasingly short supply
• Rainwater or grey water systems may become the norm
• Blue amenity space will play an increasingly important role
Planning for the future
• Create wildflower gardens with ponds and water features for animals/birds during hotter, drier, summers
• Don’t plant for the long term in flood areas• If gardening on slopes, don’t clear too much of
the existing garden as this will create problems with erosion
• Choose plants carefully and work with the gardening environment
Planning for the future
Trees, consider:
Drought impact (limb drop)Water logging (subsidence)
In warmer, wetter winters, root pathogens are more active and roots become more seriously damaged
Planning for the future
Use of Mediterranean plants and shrubs will alter the character of gardens. May suffer from unseasonable frosts.
Biodiversity affected: insects and pollinationfood chain (birds, insects etc)
The choices we make will create different outcomes
IPCCWith substantial
mitigationWithout
additional mitigation
Change in average surface temperature (1986–2005 to 2081–2100)
P.S.
The Guardian newspaper is currently publishing a series of articles on Climate Change.
See http://www.theguardian.com/environment/climate-change
Events in Ambridge
Followers of The Archers will know the problems currently facing Ambridge after unprecedented flooding when the Am burst its banks.
http://www.bbc.co.uk/programmes/articles/4gnZ0YZDdJW2NHHZ1vYz00y/uk-weather-warning-borsetshire
Carbon footprint
You can check out your own carbon footprint
See
• http://www.energysavingtrust.org.uk/domestic/
• http://carboncalculator.direct.gov.uk/index.html