diff --git a/notebooks/example-workflows/ecs-cmip6.ipynb b/notebooks/example-workflows/ecs-cmip6.ipynb
index b575cb5..9d5988a 100644
--- a/notebooks/example-workflows/ecs-cmip6.ipynb
+++ b/notebooks/example-workflows/ecs-cmip6.ipynb
@@ -311,7 +311,7 @@
     "    which can lead to issues when merging.\"\"\"\n",
     "    drop_vars = [vname for vname in ds.coords\n",
     "                 if (('_bounds') in vname ) or ('_bnds') in vname]\n",
-    "    return ds.drop(drop_vars)\n",
+    "    return ds.drop_vars(drop_vars)\n",
     "\n",
     "def open_dsets(df):\n",
     "    \"\"\"Open datasets from cloud storage and return xarray dataset.\"\"\"\n",
@@ -471,7 +471,7 @@
     "    # https://github.com/pydata/xarray/issues/2237#issuecomment-620961663\n",
     "    dsets_ann_mean = [v[expt].pipe(global_mean)\n",
     "                             .swap_dims({'time': 'year'})\n",
-    "                             .drop('time')\n",
+    "                             .drop_vars('time')\n",
     "                             .coarsen(year=12).mean()\n",
     "                      for expt in expts]\n",
     "\n",
@@ -645,14 +645,12 @@
    "source": [
     "ds_abrupt = ds_anom.sel(year=first_150_years, experiment_id=co2_option).reset_coords(drop=True)\n",
     "\n",
-    "def calc_ecs(ds):\n",
-    "    # Some sources don't have all 150 years, drop those missing values.\n",
-    "    a, b = np.polyfit(ds.tas.dropna(\"year\"),\n",
-    "                      ds.imbalance.dropna(\"year\"), 1)\n",
+    "def calc_ecs(tas, imb):\n",
+    "    a, b = np.polyfit(tas, imb, 1)\n",
     "    ecs = -1.0 * (b/a) # Change -1.0 to -0.5 if using 4xCO2\n",
     "    return xr.DataArray(ecs)\n",
     "\n",
-    "ds_abrupt['ecs'] = ds_abrupt.groupby('source_id').apply(calc_ecs)\n",
+    "ds_abrupt['ecs'] = xr.apply_ufunc(calc_ecs, ds_abrupt.tas, ds_abrupt.imbalance, vectorize=True, input_core_dims=[['year'], ['year']])\n",
     "ds_abrupt.compute()"
    ]
   },
@@ -776,7 +774,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.9"
+   "version": "3.10.15"
   },
   "nbdime-conflicts": {
    "local_diff": [