Agronomist’s guide to information for managing weather and climate risk
Author: Peter Hayman (SARDI)
Take home messages
- Advances in weather and climate science combined with advances in information and communication technology have led to extraordinary access to information.
- It is important to understand the difference between a weather forecast, a seasonal climate outlook and climate change projections. New developments such as multi-week forecasts from the Bureau of Meteorology’s model (POAMA) blur the distinction between weather and climate.
- A useful framework is to consider decisions as operational, tactical and strategic.
- Weather forecasts can be used for short term operational decisions; seasonal climate outlooks can be used for tactical decisions and long term climate information such as deciles can be used for strategic decisions.
There is an abundance of weather and climate information
We always overestimate the change that will occur in the next two years and underestimate the change that will occur in the next ten (Bill Gates, Brainy quote's website).
The last decade has seen dramatic changes in information and communication technology (ICT). Australia as a whole is an early adopter of this technology. We have 30 to 40% more mobile phone connections than we have people and we have amongst the highest per capita use of smart phones and tablets. Grain farmers and their advisers are making very different use of this technology than they were 10 years ago.
There have also been impressive gains in weather forecasts of the coming four to seven days and ongoing developments in seasonal climate forecasts and information on climate change. Sometimes accessing the large amount of information is like trying to drink from a fire hydrant.
Weather forecasts and seasonal climate outlooks
Weather is a ‘snap shot’ of the atmosphere at a particular time whereas climate is a composite of weather events. Weather is determined by the timing of individual synoptic events such as a cold front or high-pressure systems and can last between a few hours to a week. The conventional time for climate is 30 years (often the period 1960 to 1990). This distinction is important when it comes to understanding the difference between a weather and climate forecast. Weather forecasts are mostly based on numerical models; these are initiated from the current state of the atmosphere and used to predict future states of the atmosphere, including the timing and amount of rainfall for up to 10 days ahead. There is much more confidence in the first four days of the forecast than subsequent days. In Australia the Bureau of Meteorology has moved to what they describe as the next generation of forecasts, the most notable example is METEYE Bureau of Meteorology website.
In contrast, seasonal climate forecasts typically give the chance (probability) of the next 3–6 months being wetter or drier (or hotter or cooler) than the long-term average. Rather than being based on prediction from the inherently chaotic dynamics of the atmosphere, they tend to be based on patterns of the sea surface temperature (SST) or associated atmospheric characteristics. There is good scientific evidence that changes in the patterns of sea-surface temperatures have an impact on the behaviour of the atmosphere for months ahead and over widespread regions. In Australia the Bureau of Meteorology has shifted from a forecasting system based on statistical relationships between rainfall and patterns of ocean temperatures to a dynamic model called “The Predictive Ocean Atmosphere Model for Australia (POAMA)”. POAMA website GRDC has funded Dr James Risbey (CSIRO, Hobart) to work with SARDI on analysing the opportunities to forecast a change in the likelihood of heat and frost events. While the BoM is no longer using statistical approaches, other research groups in Australia are exploring the role of statistical seasonal climate forecasts.
The Managing Climate Variability Program (of which GRDC is the largest stakeholder) has funded the Centre for Australian Weather Research (CAWCR) to improve and characterise the skill of POAMA’s predictions for 2-8 weeks ahead and “make them more useful to agriculture and water management industries”. The period of 2-8 weeks starts to blur the distinction between weather and climate.
The climate system will change and evolve over time due to internal forcing. For example; El Niño events are naturally occurring shifts in energy in the tropical Pacific Ocean. A decade with a higher frequency of El Niño events can have far reaching impacts on the climate system. There are also natural external influences such as solar variations due to the orbital tilt of the earth, sunspot activity or volcanic eruptions, well understood to cause climate change. As the world warms due to the orbital tilt, the oceans release carbon dioxide which provides a positive feedback on the warming process.
Human-induced changes have occurred due to increased greenhouse gases, land use change and aerosols. The argument of climate science is that recent warming cannot be explained by internal forcing or by natural forcing and that most of the recent warming is due to greenhouse gasses released by human activity. Climate change projections for Australia are available from the CSIRO through the Climate Futures Program.
Figure 1 shows weather, seasonal climate and climate change information with different time scales (Y axis) and spatial scale (X axis).
Figure 1. Time and space scale of atmospheric phenomena (modified from WMO graphic). Both axes are logarithmic, a local severe storm may be forecast and have an impact in a radius of 10 to 100 km, whereas high pressure systems that cross Australia are 2 to 3,000 km across. The impact of ENSO is at a continent scale and as the name suggests, global warming affects the planet.
Operational, tactical and strategic decisions
A useful framework to consider decisions is to consider long term strategic decisions that set the overall direction of the farm, seasonal tactical decisions that respond to prices, the time of the break, stored soil water, disease and weed build up and potentially a seasonal climate forecast. Then in running a farm, there are day to day operational decisions. This framework is used in GRDC Business Management Fact Sheets (Making Effective Business Decisions, Making Effective Business Decisions Factsheet, July 2013; Simple and Effective Business Planning, Simple Effective Planning Factsheet, May 2014).
Taking the example of topdressing wheat, many farmers have made a strategic decision to develop management rules and invest in a quality fertiliser spreader for topdressing. There is a tactical decision of how much N to add as topdressing and then an operational decision on the timing of top dressing. This demarcation of decision partly maps across to the difference between weather for operational, seasonal climate for tactical decisions and the use of long term climate deciles for a sense of target yields. For some famers an acceptance of higher variability and uncertainty from climate change may influence the strategy of being flexible.
Weather and climate information is one bit of the jigsaw when working with clients on decisions ranging from nitrogen fertiliser to farm expansion.
SARDI Climate Applications, GPO Box 397, Adelaide SA 5000