Are we really are involved in a period of climate change?

Rainfall in WA has been decreasing over the last 25 years. Each summer we face water restrictions.Is this the prelude to Greenhouse?

The landuse practices of the past 150 years of settlement in WA have cleared millions of hectares of vegetation, replacing them with annual crops. Is this having an effect on the weather?

The Kyoto Protocol and Climate Change are firmly on the International Agenda. Many would acknowledge that these are important issues, but how are we tackling problems of climate change here in WA?

A conference held in October invited scientists from a range of fields to address these questions and produce the evidence for their understanding of our current situation. Their reports give us useful data to understand the present and plan for the future. 

Below is Part 1. of the findings:

The Indian Ocean Climate Initiative and CSIRO - Climate Expectations and Uncertainties

Decision making with an evolving climate, and how we adapt to both natural and human induced variability and change were addressed. Our records have been the best evidence we have on climate, but they are no longer good enough. We can no longer rely on past records alone to portray the future when making plans.

We have a drying climate in the SW of WA. River flows have declined by 45% over the last 25 years. Rainfall has declined by 20%; there are fewer rainy days and less rain on each rainy day. We no longer have really wet winters. It seems that a quite abrupt change has taken place in the relationships between rainfall and the El Nino Southern Oscillation. Over a 1000 year period such change could have happened naturally.

There is no uncertainty about the increase in carbon dioxide (CO2) in the atmosphere. There has been a marked increase in the last 140 years, which co-incides with the Industrial Revolution. With increase in CO2 levels has come temperature increase in the last 100 years. Most of the observed warming has occurred in the last 50 years, corresponding with the increase in Greenhouse gases.

Global temperatures and sea levels all point to continued warming and rise. Inevitably human influences will continue to change the composition of the atmosphere through the 21st century.

Of the 9 most authoritative climate models, 7 indicate reduced rainfall in the SW of WA. Our experience is that the drying is taking place faster than the models predict. Our present uncertainty is how much temperature rise and how much rainfall decline, how quickly.

Marine Ecosystems.

Marine ecosystems are important because the oceans are the heat sink of the planet. WA is a special case as the west coast is the only place in the world with a warm south flowing current. We can learn a lot from the movements of sea birds because they are at the top of the food chain and can act as biological indicators. Seabirds do not move readily, but many tropical species are moving south. Seabirds operate in fisheries and our fisheries are also changing. The rock lobster fishery is in decline even though there has been no change in management. Tropical species are now mixed with temperate species; all are sensitive to El Nino.

The frequency, intensity and length of El Nino have increased over the last 50 years. In the last two decades El Nino has operated almost every other year at the longest and strongest level. El Nino can also weaken the Leeuwin Current.

Terrestrial Ecosystems

In the SW Botanical Province there are potential impacts of climate change on biodiversity. The SW is a Global ‘Hot Spot’ for biodiversity with the amazing number of 5500 species of vascular plants. These also show a high level of local variability. Climate change can influence vegetation ranges and distribution of animals as well as plants.

Because we have huge threats posed by extensive clearing, fragmentation and salinity, climate change brings yet another massive challenge particularly to the agricultural region, where reserves of native species are small and scattered. So there are real threats to the SW biota. The problem is big as many hundreds of species will be affected. Research points to quite dire results and the urgent need to maximise the extent of conservation reserves.

We need to take the Precautionary Principle very seriously.

Other matters raised were:

The impact of fire: we don’t know how the balance between carbon dioxide (CO2) and methane (CH4) in the atmosphere is affected by fire, wildfire and prescribed burning, but both are Greenhouse gases, which we should be doing our best to limit.

The long term sustainability of large cities, such as Perth, as water becomes a limiting factor and Perth’s hinterland comes under increasing stress.