Guwahati, India - He sniffs, slurps his tea, swirls and spits a jet of orangish liquid into the tumbler.

"Malty, hard," says Parag Hatibaruah, a professional tea-taster. "But not as strong, brisk and creamy as it was once," he adds, shaking his head dismissively. Rows of teacups and packs of dried leaves are lined up neatly in the well-lit tasting room.

Assam tea used to be more pungent and full-bodied and looked like tomato soup, he says, but the unwelcome transformation started 10 years ago. "Even the sheen of tealeaves is lost."

Along with waning taste, the industry is grappling with diminishing production and reduced prices. High hills and abundant rainfall made Assam state in India's northeast the largest tea-producing region in the world. Now experts say the "ideal climate" has changed - soaring temperatures and fickle rain are choking the once-flourishing plantation industry.

India produces one-third of world's tea and about 850 gardens in Assam produce 51 percent of it. Assam tea is famous for its orthodox and CTC (crush, tear, curl) variety of black teas, which are sold as breakfast teas.

"You can't make good tea out of bad leaves, but you can produce bad tea out of good leaves," Hatibaruah says.

Evidence of change

As global temperatures inch upward, all tea-producing belts are being affected, says RM Bhagat, deputy director of the Tea Research Association, based in Tocklai. "But the degree of impact varies regionally, depending on distance from equator and other local conditions."

The Tocklai tea experimental station has been recording daily weather and tea production data for more than 100 years. "We have found that the minimum temperature has risen by 1.5 degree centigrade, and the annual rainfall has reduced by 200 millimetres," he says.

The region is battered with erratic rainfall and frequent bouts of floods and droughts. Winter rainfall has become scarce, and distribution is fluctuating. Bhagat says tea trees in Assam previously would be high yielding until 40-45 years of age, but now decline at 30-35.

"Only time will say whether the tea trees will adapt or not, but the industry has to gear up," he says. He recommends increasing shaded areas, alternative water systems, and using organic manure. The association is also testing clones that are resistant to climate change, he adds.

Weather plays spoilsport

"Assam always had sub-tropical climate, but now it has become fully tropical - affecting production," explains Prafulla Bordoloi, a tea scientist

In Assam, the usual ambient temperature used to be below 35 degrees Celsius. But now the range has shot up to 38 to 40 degrees C in shaded areas, and upwards of 50 degrees C in non-shaded spots. Photosynthesis slows at 35 degrees C, and beyond 39 degrees C food production stops. After 48 degrees C, tealeaves stop breathing and are destroyed, he says. "Often one-third of the gardens have no shade."

Prolong dry spells disturbs the flushing pattern. Along with stunted growth, increased dampness has led to an upsurge in pests. "Minor pests have become major pests. There is a spike in bugs such as the tea mosquito," Bordoloi says.

Regulation of pesticide use and environmental concerns complicate the problem. "Planters are faced with hard choices," he adds.

Production fluctuates

In 2010, Assam produced 480 million kilograms of tealeaves and 588 million kg in 2012. But this increase was attributed to an expansion in the area of production.

"Tea production from organised or corporate sector is stagnant, but that of small growers and bought leaf sector is increasing rapidly," says S Patra, joint secretary of Indian Tea Association, based in Kolkata. He says Assam tea faces "stiff competition" from Sri Lanka and Kenya.

Small tea growers contribute about 30 percent of total tea production in Assam, says Aswwini Baruah, president of Assam Small Tea Growers Association.

"Small tea growers don't have the resources to deal with climate change, but our tea trees are young, so our production is increasing, and we have not suffered loss," he says.

Apart from the change in climate, there are other factors affecting quality and plummeting prices, says Surajit Phukan, director of Eastern Tea Brokers Association. An increase in migration of labourers to high-paying sectors has resulted in a shortage of tealeave pluckers. Random and excessive use of pesticides and fertilisers has dented Assam's tea reputation on the international market.

Further, more factories are opting to process purchased leaves so the overall quantity of good Assam tea declines.

"It's a catch-22 situation for the planter - you need purchased leaves to reduce costs, and you need to make better teas to earn good prices," Phukan says.

During the 1980s, the Assam tea industry shifted its focus from quality to quantity to cater to the growing global demand for tea, he says. "Many high yielding clones were used, but flavour was lost."

Phukan says it is a challenging time for the tea industry.

This story has been written under the aegis of the CSE Media Fellowships