‘It’s an ongoing battle,’ says Simon Hilton-Smith, collections manager at the Saffron Walden Museum. ‘We’re opening all the cases, we’re cleaning everything of bugs and pests, making sure there’s enough airflow but not too much – it’s just constant vigilance at the moment.’ Like most of East Anglia, Saffron Walden barely saw a drop of rain between late June and this week, when scattered showers brought scant relief to earth parched by five successive heatwaves, with rumblings of a sixth to come in September. The town’s museum opened in 1835, making it one of the oldest purpose-built public museums in the United Kingdom. The fear now is that the climatic conditions for which it was built have changed irrevocably.

Several museums in the UK have been forced into unprecedented full or partial closures this summer to protect staff and visitors from the heat; others, blessed with air conditioning, have advertised themselves as cool havens for the public as part of the BFI and Arts Council England’s Cool Off in Culture campaign. But amid an understandable focus on the effects of extreme conditions on the people who work for and visit museums, there has been little public reflection on what a changing climate means for the ability of museums to carry out their other chief duty of care: towards their collections. At a fundamental level, the sector for conservation and care of collections depends upon a degree of ‘climate control’. What might that look like in an era of increasing climate instability?

For David Saunders – now an honorary research fellow at the British Museum, where he was head of conservation between 2005–2015 – it is important to emphasise that ‘we haven’t been caught on the hop’. Except for a few specific materials – such as wax, with which the Grant Museum of Zoology in London has been having particular problems – prolonged temperatures in the high 30s degree Celsius are not, on their own, enough to pose serious risk to collections. What matters more, Saunders says, ‘is what that heat does in terms of the moisture around it’ – ‘things can desiccate if they get too hot and there isn’t an accompanying introduction of moisture’, the monitoring of which is standard practice in museums. Rising sea levels and extreme levels of precipitation are a greater cause for concern – one which will be keenly felt in parts of the country this week, where flash floods are forecast.

As much as it may benefit staff and visitors looking for respite from the heat, aircon is no panacea in terms of collections care. Far from it – Saunders suggests that since the early 2000s there has been a move away from recommending ‘blanket, prescriptive conditions for everything’ and towards a more object-focused risk management. This approach culminated in the Bizot Green Protocol, a set of sustainability guidelines first issued by the Bizot Group of some 50 international museums in 2015, and updated in 2023. While this was explicitly geared at helping museums adopt greener practices, the research on which it was based had identified that collections could withstand a much larger range of climatic conditions than previously assumed.

In fact, where it becomes interesting for Saunders is with collections that have been subject to stricter climate controls in recent decades. ‘You think of altarpieces, which would have been in uncontrolled conditions in churches, perhaps very hot or cool or damp – but that subsequently have been structurally conserved and put back in conditions that are rather more controlled. There’s a fear, I think, that if they were then to return to uncontrolled conditions they would see dimensional changes, cracking, flaking and so forth.’

May Cassar, director of the Institute for Sustainable Heritage at University College London, likewise warns against the ‘knee-jerk reaction to air condition everything’. She suggests there is a need to better ‘understand how traditional buildings work’ – the ways that ‘buildings of traditional materials such as cob, wattle and daub, flint, lime plaster tend to maintain cooler conditions’ when coupled with ‘common sense practice of natural ventilation’ such as ‘night-time cooling, internal shutters and external awnings’. Of course, opening the windows at night brings a risk of ‘pests and pollution, which needs to be mitigated. But for Cassar, ‘Conservation cannot simply be focused on collections. There is also a responsibility to conserve the environment.’

These demands need not be in competition with one another. For Simon Hilton-Smith, rising energy bills make it imperative that ‘systemic changes’ to the planning regulations that govern buildings like the Saffron Walden Museum are made. He wants to see grey water systems in the toilets, heat pumps and solar panels – anything that cuts costs and enables the museum to ‘remain at a constant without drawing any more on the power grid’. He has on his team, he says, a volunteer who worked in conservation for 30 years; but ‘if she disappeared’, the museum would be thrust back on limited resources. Freeing up funds for staff to properly monitor the collection is paramount for local museums like this – and Hilton-Smith is keen to see more ‘top-down’ support from central government, whether that means VAT cuts, support for sustainable retrofitting or simply better guidance from DCMS on climate resilience. ‘People are worried about making the wrong decisions,’ he says.

For Ben Melham, director of Mortice Consulting which has been advising museums internationally on heatwave responses in recent months, the wider potential ramifications of global warming for museum collections are inextricable from the human cost. Staff are struggling in sweltering conditions, affecting their ability to effectively monitor their collections. There has been a pronounced drop in footfall during what is meant to be the busiest (and most profitable) time of year; even where museums do have air-con, many would-be visitors are put off by the thought of ‘getting on a really hot tube to travel into central London’. Some of the museum closures we’ve seen this summer were motivated not only by public health, but by the fact that visitors can introduce ‘erratic conditions’ that might harm collections. The effect of these long, hot summers on museums’ bottom lines is something that ‘nobody can fully quantify at the moment,’ Melham says – but it’s something that the sector ‘needs to wake up to’.