diff --git a/demo/js/ml-datasets.js b/demo/js/ml-datasets.js
index 635c0384..454ed7d1 100644
--- a/demo/js/ml-datasets.js
+++ b/demo/js/ml-datasets.js
@@ -301,7 +301,7 @@ const hedgeControlDataset = {
 const datasetsPlugin = createDatasetsPlugin({
   layerAdapter: maplibreLayerAdapter,
   globals: {
-    opacityMode: 'multiply', // 'dataset', 'global' or 'multiply'
+    opacityMode: 'dataset', // 'dataset', 'global' or 'multiply'
     opacity: 0.75,
     visible: true
   },
@@ -396,15 +396,12 @@ const testFeatureVisibility = () => {
 const testSetOpacity = () => {
   setTimeout(() => datasetsPlugin.setOpacity(0.8, { datasetId: 'land-covers' }), 500)
   setTimeout(() => datasetsPlugin.setOpacity(0.2, { datasetId: 'land-covers', sublayerId: '130-131' }), 2000)
-  // setTimeout(() => datasetsPlugin.setOpacity(0.8, { datasetId: 'land-covers', sublayerId: '130-131' }), 2000)
-  // setTimeout(() => datasetsPlugin.setOpacity(0.3, { datasetId: 'land-covers', sublayerId: '130-131' }), 2500)
   setTimeout(() => datasetsPlugin.setOpacity(0.97, { datasetId: 'land-covers' }), 4000)
-  // setTimeout(() => datasetsPlugin.setOpacity(1, { datasetId: 'land-covers', sublayerId: '130-131' }), 6000)
-
-  setTimeout(() => datasetsPlugin.setOpacity(0), 8000)
-  setTimeout(() => datasetsPlugin.setOpacity(1), 10000)
-  // TODO:
-  // setTimeout(() => datasetsPlugin.setGlobal({ opacityMode: 'multiply' }), 2000)
+  setTimeout(() => datasetsPlugin.setOpacity(0), 6000)
+  setTimeout(() => datasetsPlugin.setGlobals({ opacityMode: 'global' }), 7000)
+  setTimeout(() => datasetsPlugin.setOpacity(0.8), 7500)
+  setTimeout(() => datasetsPlugin.setGlobals({ opacityMode: 'dataset' }), 8000)
+  setTimeout(() => datasetsPlugin.setGlobals({ opacityMode: 'multiply' }), 9000)
 }
 
 const testSetStyle = () => {
diff --git a/plugins/beta/datasets/src/api/setGlobals.js b/plugins/beta/datasets/src/api/setGlobals.js
new file mode 100644
index 00000000..10195266
--- /dev/null
+++ b/plugins/beta/datasets/src/api/setGlobals.js
@@ -0,0 +1,20 @@
+import { logger } from '../../../../../src/services/logger.js'
+export const setGlobals = ({ pluginState: { dispatch } }, values) => {
+  const { opacityMode } = values
+  const payload = {}
+  let valuesSet = false
+  if (opacityMode) {
+    if (!['dataset', 'global', 'multiply'].includes(opacityMode)) {
+      logger.warn(`Ignoring invalid opacityMode: ${opacityMode}. Must be one of 'dataset', 'global' or 'multiply'.`)
+    } else {
+      valuesSet = true
+      payload.opacityMode = opacityMode
+    }
+  }
+
+  if (valuesSet) {
+    dispatch({ type: 'SET_GLOBAL_STATE', payload })
+  } else {
+    logger.warn('setGlobals: requires a valid value for opacityMode to be set')
+  }
+}
diff --git a/plugins/beta/datasets/src/api/setGlobals.test.js b/plugins/beta/datasets/src/api/setGlobals.test.js
new file mode 100644
index 00000000..bb0e1651
--- /dev/null
+++ b/plugins/beta/datasets/src/api/setGlobals.test.js
@@ -0,0 +1,63 @@
+import { setGlobals } from './setGlobals.js'
+import { logger } from '../../../../../src/services/logger.js'
+
+jest.mock('../../../../../src/services/logger.js', () => ({
+  logger: { warn: jest.fn() }
+}))
+
+describe('setGlobals', () => {
+  const dispatch = jest.fn()
+
+  beforeEach(() => {
+    jest.clearAllMocks()
+  })
+
+  it('dispatches SET_GLOBAL_STATE with opacityMode when valid value is provided', () => {
+    setGlobals({ pluginState: { dispatch } }, { opacityMode: 'dataset' })
+
+    expect(dispatch).toHaveBeenCalledWith({
+      type: 'SET_GLOBAL_STATE',
+      payload: { opacityMode: 'dataset' }
+    })
+  })
+
+  it.each(['dataset', 'global', 'multiply'])('accepts valid opacityMode: %s', (opacityMode) => {
+    setGlobals({ pluginState: { dispatch } }, { opacityMode })
+
+    expect(dispatch).toHaveBeenCalledWith({
+      type: 'SET_GLOBAL_STATE',
+      payload: { opacityMode }
+    })
+    expect(logger.warn).not.toHaveBeenCalled()
+  })
+
+  it('warns and does not dispatch when opacityMode is invalid', () => {
+    setGlobals({ pluginState: { dispatch } }, { opacityMode: 'invalid' })
+
+    expect(logger.warn).toHaveBeenCalledWith(
+      "Ignoring invalid opacityMode: invalid. Must be one of 'dataset', 'global' or 'multiply'."
+    )
+    expect(dispatch).not.toHaveBeenCalled()
+  })
+
+  it('warns and does not dispatch when no valid values are provided', () => {
+    setGlobals({ pluginState: { dispatch } }, {})
+
+    expect(logger.warn).toHaveBeenCalledWith(
+      'setGlobals: requires a valid value for opacityMode to be set'
+    )
+    expect(dispatch).not.toHaveBeenCalled()
+  })
+
+  it('warns about invalid opacityMode and then warns no valid values set', () => {
+    setGlobals({ pluginState: { dispatch } }, { opacityMode: 'bad' })
+
+    expect(logger.warn).toHaveBeenCalledWith(
+      "Ignoring invalid opacityMode: bad. Must be one of 'dataset', 'global' or 'multiply'."
+    )
+    expect(logger.warn).toHaveBeenCalledWith(
+      'setGlobals: requires a valid value for opacityMode to be set'
+    )
+    expect(dispatch).not.toHaveBeenCalled()
+  })
+})
diff --git a/plugins/beta/datasets/src/datasets.js b/plugins/beta/datasets/src/datasets.js
index 8d024a63..6d5f0ad5 100644
--- a/plugins/beta/datasets/src/datasets.js
+++ b/plugins/beta/datasets/src/datasets.js
@@ -18,7 +18,7 @@ export const createDatasets = ({
   const dynamicSources = new Map()
 
   if (pluginConfig.globals) {
-    dispatch({ type: 'INITIALISE_GLOBAL_STATE', payload: pluginConfig.globals })
+    dispatch({ type: 'SET_GLOBAL_STATE', payload: pluginConfig.globals })
   }
 
   // Initialise all datasets via the adapter, then set up dynamic sources
diff --git a/plugins/beta/datasets/src/manifest.js b/plugins/beta/datasets/src/manifest.js
index c1fbadd8..bb33ee5e 100755
--- a/plugins/beta/datasets/src/manifest.js
+++ b/plugins/beta/datasets/src/manifest.js
@@ -12,6 +12,7 @@ import { getStyle } from './api/getStyle.js'
 import { setOpacity } from './api/setOpacity.js'
 import { getOpacity } from './api/getOpacity.js'
 import { setData } from './api/setData.js'
+import { setGlobals } from './api/setGlobals.js'
 
 export const manifest = {
   InitComponent: DatasetsInit,
@@ -118,6 +119,7 @@ export const manifest = {
     getStyle,
     setOpacity,
     getOpacity,
-    setData
+    setData,
+    setGlobals
   }
 }
diff --git a/plugins/beta/datasets/src/reducer.js b/plugins/beta/datasets/src/reducer.js
index 4c43e3df..bb49c00e 100755
--- a/plugins/beta/datasets/src/reducer.js
+++ b/plugins/beta/datasets/src/reducer.js
@@ -34,9 +34,13 @@ const validateDatasetExists = (state, datasetId, prefix, suffix = 'not found') =
   return true
 }
 
-const initialiseGlobalState = (state, payload) => {
+const setGlobalState = (state, payload) => {
+  // For now we only have opacityMode, but if we add more global state
+  // properties we may not require applyGlobalOpacity to be triggered here.
+  const applyGlobalOpacity = [...state.layerAdapterActions.applyGlobalOpacity, []]
   return {
     ...state,
+    layerAdapterActions: { ...state.layerAdapterActions, applyGlobalOpacity },
     globals: { ...state.globals, ...payload }
   }
 }
@@ -181,7 +185,7 @@ const setOpacity = (state, payload) => {
 
 const setGlobalOpacity = (state, payload) => {
   const { opacity } = payload
-  const applyGlobalOpacity = [...state.layerAdapterActions.applyDatasetOpacity, []]
+  const applyGlobalOpacity = [...state.layerAdapterActions.applyGlobalOpacity, []]
   return {
     ...state,
     layerAdapterActions: { ...state.layerAdapterActions, applyGlobalOpacity },
@@ -204,7 +208,7 @@ const actions = {
   SHOW_FEATURES: showFeatures,
   SET_LAYER_ADAPTER: setLayerAdapter,
   SET_LAYER_ADAPTER_ACTIONS: setLayerAdapterActions,
-  INITIALISE_GLOBAL_STATE: initialiseGlobalState
+  SET_GLOBAL_STATE: setGlobalState
 }
 
 export {