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Displaying items by tag: climate change

Have you ever enjoyed the cool refuge that an underground cave offers from a hot summer’s day? Or perhaps you have experienced the soothing warmth when entering a cave during winter?

When descending into a cave, you may not only enjoy the calm climate, you may also admire the beauty of cave deposits such as stalagmites, stalactites and flowstones, known by cave researchers as speleothems.

Perhaps you already know that they grow very slowly from minerals in the water that drips off or over them. This water originates from rain at the surface that has travelled through soil and limestone above, and seeped into the ground and ended up in the cave.

As speleothems grow, they lock into their minerals the chemical signatures of the environmental and climatic conditions of the time the rainwater fell at the surface. So, as a stalagmite grows, the surface climate signature is continuously trapped in the newly created layers.

Some very old stalagmites hold climatic signatures of the very distant past, in some cases up to millions of years. They contain an archive of the past climate as long as their age, often predating global weather station records.

Above and Below

But if a cave remains cool during summer and warm during winter, how is its climate related to that of the surface? And how does this affect the chemical signature recorded by speleothems?

To understand the relationship between surface and cave climate, our research group, Connected Waters Initiative Research Centre at UNSW Australia, conducted multiple field experiments at the Wellington Caves Reserve in New South Wales.

During the experiments, the surface and the cave climates were measured in detail. For example, highly accurate temperature sensors were used to measure the water temperature at the surface, and at the point where water droplets hit the cave floor forming stalagmites.

cave

Installation of high-resolution temperature sensors inside the cave. Martin S Andersen

The research team initiated controlled dripping in the cave by irrigating the surface above the cave with water that was cooled to freezing point to simulate rainfall.

The cold water allowed us to determine whether the drip water in the cave is affected by the conditions at the surface or those along its pathways through the ground.

We also added a natural chemical to the irrigation water, which allowed us to distinguish whether the water in the cave originated from the irrigation or whether it was water already present in the subsurface.

Our results revealed a complex but systematic relationship between the surface and the cave climate. For example, surface temperature changes are significantly reduced and delayed with depth.

Our research illustrates how to decipher the surface temperature from that in the cave. Understanding this is necessary to correctly decoding past surface temperature records from their signatures preserved in stalagmites.

Keeping it Cool

We also discovered that air moving in and out of the cave can cool cave deposits by evaporating water flowing on the cave deposits. This cooling can significantly influence the chemical signature trapped in the cave deposit and create 'false' signals that are not representative of the surface climate.

In other words, it will make the surface climate 'look' cooler than it actually was, if not accounted for. While this is more likely to occur in caves that are located in dry environments, it may also have to be considered for stalagmites in caves that were exposed to drier climates in the distant past.

Our new knowledge can also help scientists select the best location and type of stalagmite for the reconstruction of past climatic or environmental conditions.

This new discovery is significant because it can improve the accuracy of past climate signals from cave deposits. It may also help us understand previously unexplained artefacts in existing past climate records. By improving our understanding of the past climate we can better understand future climate variations.

(The ConversationPhoto at the top of page is of temperature loggers installed on stalactites to measure the drip water temperature. Martin S Andersen)

Gabriel C Rau, Associate Lecturer in Groundwater Hydrology, UNSW Australia; Andy Baker, Director of the Connected Waters Initiative Research Centre, UNSW Australia; Mark O Cuthbert, Research Fellow in Hydrogeology, University of Birmingham, and Martin Sogaard Andersen, Senior lecturer, UNSW Australia

This article was originally published on The Conversation. Read the original article.

Published in STEP Matters 188

Well the July election is done and dusted and the Liberal–National Coalition just scraped in. Despite Malcolm Turnbull’s previous statements about the need for serious action on climate change it appears that he does not have the political will to overturn past government decisions to downgrade climate change research and development.

CSIRO Cuts

CSIRO is an organisation independent from the government but still very much dependent on government funding. In February the CEO announced that climate science is settled so the focus can change to adaptation and mitigation. This statement was used to justify cutting over 100 climate change research jobs. Funding could be diverted to fields that could be more lucrative.

The size of the cuts was modified following an international outcry but there was still a cut of about 75 positions from the Oceans and Atmosphere division. Research is to be centred in Hobart in a new Climate Science Centre that will coordinate the work of 40 scientists carved out of existing CSIRO teams, and also tap into work by the Bureau of Meteorology and universities.

In August another modification was made when new Science Minister, Greg Hunt, ordered CSIRO to revive some other climate science programs in climate analysis and forecasting in Hobart. But these jobs will be financed out of the existing budget.

Fundamentally we still have less climate science capacity than before the cuts were announced. Some outstanding scientists with a huge accumulation of knowledge such as John Church, global sea level expert, will not return.

Support for Renewable Energy

There are plans to cut most of the funding for Australian Renewable Energy Agency as well as its ability to give grants. As the world responds to the urgent need to build new renewable electricity generation capacity, this plan is puzzling. Again the government’s reason is long-term ‘budget repair’. Australia has a long history of leading research into new solar technology. Hundreds of jobs will be lost from current research organisations and the potential opportunities for future commercialisation.

These policies conflict with the plans to help Australia become an innovation nation. The message from the government is that research is an expensive luxury rather an essential part of our long-term future.

Published in STEP Matters 187

Mark Diesendorf, UNSW Australia

Can Australians be sustainable and enjoy endless economic growth? It’s not likely.

Published in STEP Matters 184
Wednesday, 03 February 2016 18:05

Paris Climate Change Agreement

The Paris climate change talks in December 2015 produced an agreement hailed as 'historic, durable and ambitious'. Developed and developing countries alike are required to limit their emissions to achieve an objective of limiting average global temperature increases to 2°C with an aspiration of 1.5°C.

Published in STEP Matters 184
Wednesday, 03 February 2016 18:00

Climate Change Implications for Local Bushland

The Ku-ring-gai Bushcare Association is an unincorporated organisation that is supported by Ku-ring-gai Council which supports the Bushcare volunteer program and holds regular educational events. The committee comprises elected volunteers and Council employees.

Published in STEP Matters 184
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