The foliage on native plants in Australia's arid zones is boosted by CO2

Increased levels of carbon dioxide (CO2) have helped boost green foliage across the world’s arid regions over the past 30 years through a process called CO2 fertilisation, according to CSIRO research.

In findings based on satellite observations, CSIRO, in collaboration with the Australian National University (ANU), found that this CO2 fertilisation correlated with an 11 per cent increase in foliage cover from 1982-2010 across parts of the arid areas studied in Australia, North America, the Middle East and Africa, according to CSIRO research scientist, Dr Randall Donohue.

"In Australia, our native vegetation is superbly adapted to surviving in arid environments and it consequently uses water very efficiently," Dr Donohue said. "Australian vegetation seems quite sensitive to CO2 fertilisation.

The fertilisation effect occurs where elevated CO2 enables a leaf during photosynthesis, the process by which green plants convert sunlight into sugar, to extract more carbon from the air or lose less water to the air, or both.

This, along with the vast extents of arid landscapes, means Australia featured prominently in our results."

"While a CO2 effect on foliage response has long been speculated, until now it has been difficult to demonstrate," according to Dr Donohue.

"Our work was able to tease-out the CO2 fertilisation effect by using mathematical modelling together with satellite data adjusted to take out the observed effects of other influences such as precipitation, air temperature, the amount of light, and land-use changes."

The fertilisation effect occurs where elevated CO2 enables a leaf during photosynthesis, the process by which green plants convert sunlight into sugar, to extract more carbon from the air or lose less water to the air, or both.

If elevated CO2 causes the water use of individual leaves to drop, plants in arid environments will respond by increasing their total numbers of leaves. These changes in leaf cover can be detected by satellite, particularly in deserts and savannas where the cover is less complete than in wet locations, according to Dr Donohue.

"On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forestry and agriculture in such areas; however there will be secondary effects that are likely to influence water availability, the carbon cycle, fire regimes and biodiversity, for example," Dr Donohue said.

"Ongoing research is required if we are to fully comprehend the potential extent and severity of such secondary effects."

This study was published in the US Geophysical Research Letters journal and was funded by CSIRO's Sustainable Agriculture Flagship, Water for a Healthy Country Flagship, the Australian Research Council and Land & Water Australia.

Reprinted from CSIRO

Donohue, R. J., M. L. Roderick, T. R. McVicar, G. D. Farquhar. 2013 "Impact of CO₂ fertilization on maximum foliage cover across the globe's warm, arid environments. Geophys. Res. Lett. 40, doi:10.1002/grl.50563

Non-deciduous perennials are responding better than deciduous, annual and ephemeral plants

Here is the abstract from a previous paper by Dr Donohue (my paras):

Using Advanced Very High Resolution Radiometer data spanning 1981–2006 and calibrated for long-term analyses of vegetation dynamics, we examine whether vegetation cover has increased across Australia and whether there has been a differential response of vegetation functional types in response to changes in climatic growing conditions. Trends in vegetation cover are interpreted within Budyko's energy – water limitation framework.

Results from an Australia-wide analysis indicate that vegetation cover (as described by the fraction of Photosynthetically Active Radiation absorbed by vegetation; fPAR) has increased, on average, by 0.0007 per year – an increase of ∼8% over the 26 years. The majority of this change is due to a 0.0010 per year increase in persistent fPAR (representing nondeciduous perennial vegetation types; up 21%).

In contrast, recurrent fPAR (representing deciduous, annual and ephemeral vegetation types) decreased, on average, by 0.0003 per year (down 7%), the trends of which are highly seasonal.

Over the same period, Australian average annual precipitation increased by 1.3 mm yr−2 (up 7%).

A site-based analysis using 90 long-term meteorological stations with minimal localized land-cover changes showed that energy-limited sites where total fPAR increased generally experienced decreases in precipitation, and water-limited sites that experienced decreases in cover were almost always associated with decreases in precipitation.

Interestingly, where vegetation cover increased at water-limited sites, precipitation trends were variable indicating that this is not the only factor driving vegetation response. As Australia is a generally highly water-limited environment, these findings indicate that the effective availability of water to plants has increased on average over the study period. Results also show that persistent vegetation types have benefited more than recurrent types from recent changes in growing conditions.

Regardless of what has been driving these changes, the overall response of vegetation over the past 2–3 decades has resulted in an observable greening of the driest inhabited continent on Earth.

Current weather emergencies in Australia

The ABC website lists the current emergencies relating to weather events.  The entire eastern half of the huge state of Queensland in northern Australia, the western half of Victoria in the south east of Australia and important areas of Western Australia are badly affected by floods and cyclones.  Eastern Victoria and south western Western Australia have been affected by bushfires, which, while burning homes and large areas of land, are not significant enough to be listed on this page:

David Karoly Speaks on Queensland Floods and Climate Change

Professor David Karoly, a world-renowned climate change expert from The University of Melbourne, is on ABC News 24 at the moment. He is describing the effect of the very strong La Nina on Queensland, combined with the record high sea surface temperatures. According to Prof Karoly, conditions now are similar to the conditions in 1974, except the oceans are warmer because of global warming. That is why the floods of 2010-2011 are worse than the floods of 1974.

This is only the second time I've seen this strong message on television, explaining the unprecedented flooding in Queensland. The first time was David Karoly as well. Given his experience - he is very brave and I have the utmost admiration for him speaking out so clearly with such strong messaging.

Let us hope that more and more people get the message.

Melbourne's long summer draws to an end

Six weeks into autumn and Melbourne's record run has ended. The 123-day run of temperatures of 20C or more had it's last day on 10 April, just over four months from when it first began. Yesterday (11 April) the temperature reached a maximum of 18.2C at midnight. Today's maximum was 17.6C at 1:00 pm.

The previous record run in 2000-01 lasted just over two and a half months (78 days), so this summer was quite exceptional.

Hobart's record run of temperatures of 17C or more ended on 2 April, lasting 105 days compared to the previous record of 72 consecutive days. This is only the seventh time since records began that Hobart has had 50 or more consecutive days with a maximum of 17C or more.

Melbourne beats record warm days by >50%

A couple of weeks ago I posted here about Melbourne's record 100 consecutive days of 20C or more. The previous record was in 2000-01 when it had 78 consecutive days at 20C or warmer. That's just over two and a half months of consistently warm weather.

Today will make it 118 days (nearly four months), which beats the previous record by 51%, which is almost one and a half months more. And theforecast for the next 7 days shows it isn't over yet.

It's still warm(ish) in Hobart, Tasmania

The other day I posted about Melbourne having a record 100 days where the maximum temperature was over 20C. Now it's 108 days and still counting, that's 30 days more than the previous stretch.

Down in Hobart they've had a record spell of warmer than normal weather as well. Here is some of what the Bureau has to say:

Come Saturday, Hobart should have had 100 consecutive days where the temperature reached at least 17 °C. This is easily the longest run of such mild weather recorded in Hobart, where comparable records extend back to 1895. It is common to have mild weather interrupted by a few cool days, even in summer. 20 °C is forecast for both Friday and Saturday, and the run of mild weather is forecast to continue into next week.

On 17 December 2009, the temperature in Hobart reached only 12.4 °C. But since then the coldest day has been 17.4 °C on 27 February — the hottest was 38.3 °C on New Year's Eve.

The previous longest stretch of such mild weather saw 72 consecutive days with the temperature reaching 17 °C from 7 December 2002 to 16 February 2003. On only 7 occasions in Hobart's climate record have there been 50 consecutive days over 17 °C — ending in 1900, 1961, 1972, 1979, 2001, 2003 and now 2010.

Hobart's average daily maximum temperature from December 2009 to March 2010 so far has been 23.0 °C, over 2 °C above the long-term average of 20.9 °C for those 4 months, and likely to be a record.

100 day warm record for Melbourne

Melbourne has broken yet another climate record. Last November (2009), the extended heatwave meant that the average temperature for the month was 5.3C above the 1961-1990 average (that's 9.5F for those still on the old scale). The average minimum was 3.9C above the 1961-1990 average minimum. That's for a whole month. Pretty incredible.

Now Melbourne has just had 100 straight days of temperatures higher than 20C, and it's not over yet. Now anyone who knows Melbourne knows how unusual that is, you don't need to go to the records. But if you do go to the records, the closest it's come in the recorded past is 78 days in 2000-01. By the way, the recorded past goes back to 1855.

Something is happening in the State of Victoria. It's called climate change and in Melbourne it's warming!