David Bruer has been growing vines and making wine at his Temple Bruer vineyard in the Mount Lofty Ranges in South Australia since 1978.

In his vineyard laboratory, weather records for every vintage for nearly 40 years are stacked in plastic folders.

David Bruer says they've brought their harvest forward by a month. ( Four Corners )

They clearly show a steady increase in maximum temperatures over that time of about 1 degree. It might seem like a relatively small change but the impact has been dramatic.

Harvested fruit is turning up hotter. The sugar levels are higher and the vintage now has to be picked earlier.

"Thirty-four years ago we used to pick in the middle of March," he said.

"We're now picking in the middle of February."

Graziers, fruit growers on the front line of change

The world is getting warmer and from the farm gate to the boardroom Australian businesses are no longer waiting for the politicians to decide if climate change is real. They're acting now.

In fact wine — one of our most celebrated crops — happens to be one of the most sensitive to environmental changes.

Last year was the third hottest year ever recorded in Australia and this year, NASA announced the five hottest years on earth on record had occurred since 2010.

It's a conclusion drawn from painstaking, technically advanced research, but increasingly Australian farmers are watching their own simpler weather charts with growing concern.

Many are now too busy adapting to this new climate reality to wait for our political leadership to deliver effective policy responses.

Over the past few months, Four Corners has travelled across the country to gauge how Australians are adapting. Graziers, fruit growers and winemakers are among those feeling the impact.

Brown Brothers were climate sceptics, once

Sorry, this video has expired Brown Brothers moves part of its operation to Tasmania

About 800 kilometres to the east of Temple Bruer, Ross Brown from Brown Brothers Wines has an even longer weather record on file.

His family has been making wine in Milawa, Victoria, for almost 130 years.

Mr Brown says he used to be a climate change sceptic but his vintage charts are indicating things have changed.

In Milawa, Brown Brothers is also picking earlier and their records show temperatures are rising.

Some of the cool climate varieties his family always used to grow here — like pinot noir and sparkling whites — have now become too unreliable so the company has moved some of its operation to cooler country in Tasmania.

"We decided that we would do our planning in future on a two-degrees increase in our vineyard temperatures and that we would have less water available," Mr Brown said.

"Making a strategic decision has really changed the way we look at our vineyards."

But if average temperature rises go beyond two degrees then, he says, the options run out.

"We don't know where to go after Tasmania," he said.

Brown Brothers is a big operation. Their winemaking is on an industrial scale and the decision to adapt to the changing weather was driven by the company's board.

Corporate Australia has been warned

It's a shift being seen in boardrooms around the country. Corporate Australia has been warned. The changing climate is something they can no longer ignore.

Last November, Geoff Summerhayes, an executive member of the Australian Prudential Regulation Authority (APRA), told businesses climate change posed a material risk to the entire financial system.

His message was that boards and directors had a fiduciary duty to their shareholders to take it into account. He cited legal opinion that found company directors who failed to consider and disclose climate risk could be in breach of the Corporations Act.

"Climate change and society's responses to it are starting to affect the global economy," he said.

"Institutions that fail to adequately plan for this transition put their own futures in jeopardy, with subsequent consequences for their account holders, members or policy holders."

That's a view that's now been backed by Reserve Bank governor Philip Lowe.

On February 16, he told a sitting of the Federal Parliament's economics committee that the Council of Financial Regulators - a body he chairs - had established a working group to look at issues about disclosure.

The RBA confirmed it believed investors needed to be given more information on climate risk.

It might seem a small move but it's seen as highly significant in the corporate world.

Former treasury economist Sam Hurley is a specialist in corporate climate risk. He says the moves by the regulators send a powerful message.

"The RBA and APRA, they're big institutions. They don't take steps lightly. They're not talking about climate on a whim," he said.

"They've studied the evidence, they've looked at what their counterparts are doing internationally, and they've looked at the trends and risks in Australia, and they've decided that now's the time to raise the bar."

For Australian business, business as usual is no longer an option.

Watch Michael Brissenden's investigation, Weather Alert, tonight on Four Corners at 8.30pm on ABC TV and on ABC iview.