"We have seen floods and severe droughts which has caused extensive damage to agricultural outputs in many countries including Sri Lanka."
"The monsoons in Sri Lanka can no longer be predicted accurately, and the two quality seasons we enjoy have not brought about good seasonal quality, for a few years," John Keells said.
The brokers said the rise in temperature has given way to much hotter weather conditions.
"The warmer weather, Sri Lanka has experienced this year at higher elevations could be a significant factor for the increase in tea production from these elevations, despite an overall drop in Sri Lanka's tea crop," they said in a report.
"It has perhaps also constrained the level of quality, and the high quality of 'Ceylon Tea' appears to be under threat."
John Keells said it is believed that rising temperatures over the next couple of decades will have serious consequences on Sri Lanka’s dry zone agriculture.
"This thinking is shared by many countries, where climate change will have an impact on most agricultural crops including tea production with suitable lands being pushed into higher elevations."
The brokers noted that in Kenya climate change is expected to drastically affect tea production over the next 40 years.
At a recent tea convention in Mombasa, a presentation on the effects of climate change demonstrated that by the year 2050, nearly all of the tea growing areas west of the Rift Valley will be unsuitable for tea growing, they said.
This represents nearly 60 percent of the tea production in Kenya, including the popular Kericho district.
John Keells also noted that with climate change, the United Kingdom has started growing tea in parts of the country where the weather has turned warmer.
"In the long term, this could pose a threat to the large volume of tea that is imported into the UK annually," they said.
The first tea plantation in Tregothnan Estate in Cornwall, South West of England which is the country's warmest region was established in 1999.
It made its first harvest in 2005 and since then production has continued to improve with a record harvest of over 10 tons expected this year, John Keells said."Could this be the beginning of a shift in the global tea cultivation map?" the brokers asked.