4 November 2021

How do you measure climate change?

Learn how records from everyday people can help protect our planet from climate change.

By Cecily Nowell-Smith

Field of colourful flowers and long green grass

Kew’s collections tell us incredible stories of botanists who travelled huge distances and engaged in complex scientific work to discover more about the plants that share our world.

Our collections also show how a person with a curious mind can contribute to our understanding of environmental history from their own back yard.

History Day

Today, 4 November 2021, is History Day.  

Organised by the Institute of Historical Research and Senate House Library, History Day is an annual event that links people interested in history to historical collections in the UK and beyond.

This year’s theme is Environmental History, which explores "collections that capture the experiences of ordinary people, collectors and scientists, looking at nature, landscape, climate change and much more."

Research into environmental history is crucial to Kew’s work developing nature-based solutions to biodiversity loss and climate change.

The records from people across the world who helped identify plants and collect specimens not only show us how our natural world has changed, but also help us develop strategies to combat those changes.

An old book open in the library
Book from Kew’s Library and Archives collection which spans 2,000 years of plant knowledge and discovery © RBG Kew

VIP: Frank Nigel Hepper (1929 — 2013)

Frank Nigel Hepper (he went by Nigel) was a Kew botanist and specialist in West African plants, who eventually became Assistant Keeper of the Herbarium

He was a great enthusiast who turned his intellectual curiosity to many topics: not only writing on botany and the history of Kew, but also people's memories of the world wars, bible plants and even Egyptology.

As someone who loved to observe the natural world, Nigel started making a periodic record of plants in the garden at his home in Leeds when he was 17 years old. 

Nigel Hepper in a black suit standing in front of a wooden book case
Photo of Nigel Hepper in 1992, when he was president of the Kew Guild © RBG Kew

Year-on-year observations

Phenological records are records of natural phenomena that occur on a regular schedule, usually annual.

For example, a year-on-year record of the date when a certain tree’s leaves first fall, or when a species of birds set off on their annual migration.

Even Groundhog Day in the US is a form of phenological observation!

You might have heard people saying things like “my tomatoes are ripening slowly this year”. By writing down the exact date when those tomatoes finally ripen, year after year, we can produce a phenological record.

These records are helpful when they are taken for several successive years.

We can combine our observations of the timing of natural phenomena with temperature and rainfall data to get a picture of climate trends.

We can also see how the plants and animals under observation have been responding to climatic changes over the years.

This is particularly useful for scientists like ours who are focusing on how cultivated plants can be adapted to climate change.

Black sign for Malus floribunda
Malus floribunda, the Japanese flowering crabapple, flowers between March and May, Andrew McRobb © RBG Kew

Flowering event

Our library contains three sets of phenological records from Nigel Hepper.

He made observations in his garden at home; first at his parents’ house in Leeds (1946-63), and then at his garden in Petersham and later Richmond (1960-2006).

We also have records he made at Kew Gardens in 1953-73 under the evocative name “Commencement of flowering”.

Nigel chose to record the first-flowering date for the plants in his study (or in some cases the first leaf or fruit) as he felt that was the simplest thing to identify consistently. 

In 2002, he analysed the data in his records and noticed what he called “rhythms” in how various plants responded to each year’s weather, and also a longer trend over time in many plants.

This trend was towards earlier flowering, which was particularly noticeable among spring-flowering plants.

It was not just evidence of climate change, but of how climate change affected different species in different ways.

Black sign for Winter jasmine (Jasminum nudiflorum)
Winter jasmine (Jasminum nudiflorum) flowers between October and December, Andrew McRobb © RBG Kew

A record of climate change

Nigel Hepper was part of a wave of like-minded scientists across Europe who demonstrated that the simple act of periodically recording first-flowering dates was valuable science.

At the time of his findings, phenology had become unpopular — it was seen as an old-fashioned hobby rather than a scientific endeavour, and official phenological records were no longer being made in the UK.

If Nigel had not made such meticulous personal records, there would be very little data for the UK during this part of the mid-20th century – exactly the period when man-made climate change started to show its most pronounced effects.

White to pink flowers of Viburnum fragrans or Viburnum farreri
Viburnum fragrans, or Viburnum farreri, showed extreme variations, flowering between October and February, Andrew McRobb © RBG Kew

Get involved

While Nigel Hepper was also a skilled botanist, phenology is a form of scientific research that almost anyone can do.

You just need to be able to consistently identify specific plants, whether in your garden, the wild or a public park, and maintain records for several years.

So get outside, take a look at the plants around you, and start jotting down what you see. You never know, your records could help protect the future of our plants, people and planet.

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